A few years back, the RMB started wearing out a bit by sporadically having days when it would double-click when you intended to single-click. With extreme care, it was possible on such days to still use it to click, though you'd have to be patient (or resort to doing it via the laptop trackpad instead). Maybe it was all the Blender usage ;)
Then, at some point (perhaps about 1-1.5 years ago), the MMB also started to occasionally act up a bit. You see, this mouse has one of those scrollwheels with a "tilt" feature, where supposedly tilting the scrollwheel side to side could be also used for certain other actions (though with default drivers, these do nothing; On a side note, my prior experience with the Logitec drivers for this mouse was that they were more trouble than they were worth, as they ended up remapping the MMB in a way that Blender couldn't see it). Once again, this is not a biggie, since it was generally sporadic in nature, and could be worked around by simply pressing heavily on the button, or tilting it to either side and then clicking.
Finally, things came to a head this past week: All of a sudden, not only did the MMB start to frequently refuse to click (even when tilted and/or pressure applied), but the LMB also started randomly double-clicking. Randomly misfiring RMB is something that we can work around. MMB not working from time to time is also workable (though just a bit clumsier/slower for some stuff). But LMB frequently misfiring is a different matter: accidental double or triple-clicks can be deadly (e.g. once upon a time, I managed to trigger a virus-laden file while trying to clean out a trove of temp files; cleaning that one out took months, and only happened after I learnt from a friend about the msconfig "Startup" tab ;)
To cut a long story short. after checking out the various options, the field was whittled down to 2 choices: the 1) Logitec G400S, and the Logitec M325 (IIRC).
I ended up going with the G400, despite not initially looking for a gaming mouse (or even one with more than the standard button). It boiled down to the following factors:
* Firstly, of all the mice I came across, only these two were of a decent size and felt comfortable to hold. I've never been a fond of those dinky "laptop mice", which are made to be small, poky, and have horrid little short retractable cords (if they still have a cord). Having used a friend's one while working on a group project to fix a badly-tangled UML diagram by hand (an especially fun exercise when two of you try to control it at the same time), I can say that trying to move a little prism around with your fingers held in a pincher-grip isn't exactly all that comfortable. So, bigger is better was obviously going to be a major factor
* The second factor in this was the fact that the M325 had one of those fancy infinite scroll wheels. Given the type of stuff I often do (i.e. doing a lot of actual clicking with that, and actually liking to "click" it to adjust some settings), I wasn't that sure whether it would end up causing me quite a lot of grief, this didn't seem like such a great idea. Of course, for just random web browsing with long-page scrolling, this could be nice, though edge-scrolling on my trackpad does the job even better in that case (Note: yes, I've reverted back to edge-scrolling, configured so that scrollbar movement direction follows the scroll direction (aka not the "natural" scrolling done on tablets) since I found the two-finger gesture too tiring on this machine)
* Finally, the corded vs wired issue. As it stands, I'm still not that comfortable with the notion of primary input devices being wireless (i.e. a wireless keyboard is 100% off the table; the security implications of that setup alone should send shivers down your spine), and also not that fond of anything that's going to have a battery I have to remember to recharge/replace or risk having it die in the middle of something, sending some command ad-infinitum. So far, I'm still more happy with corded mice than uncorded, so this was another strike against the M325.
Having said all that, the M325 did have a few things going for it. In particular, being able to be used ambidextrously, and not having extra buttons which I probably wouldn't get around to making use of (we'll see about that one... in a few weeks, I may consider trying to map volume controls to the side buttons as an experiment). Oh, and perhaps when using it wirelessly it might be feasible to use it as a hand-held remote shutter release when doing teethered shooting (something I resorted to yesterday, as I've run out of free space on my CF cards again.)
On a side note, I also managed to score a 32gb 60mb/s Sandisk CF card at the same time. Usually, these would be hard to come by in other shops, as even if the have CF cards (a major if), most are too small to be of much use(i.e. most are 4gb, while I've found 16gb + to be practical) and speed (30mb/s is bare minimum despite being problematic at times, while 60mb/s is what I actually need). Here, there was just one of 'em in the whole store. The best part though, was that I ended up getting it much cheaper than I'd expected - a whole 80 NZD cheaper than the price they originally had on the box, and 45 NZD cheaper than at the photo store I usually go to (which already has the best prices around town, despite being located in one of the most expensive/posh areas). Go Harvey Norman, the same place I got my Toshiba from! :)
Now, about the G400s. I've been testing it out this evening on a number of different tasks I do quite often, and it seems fit the bill quite nicely. It's a nice comfortable size, shape, and weight to hold and use.
The first thing I noticed after plugging it in is just how much smoother the pointing experience is with this mouse. It's like it just glides around in a silky smooth manner - not just on screen, but also across the table. At least in initial tests in Paint, it seemed to work quite well for drawing lines and circles, though further testing will still be needed to assess how easy it is to control when trying to do fine placement of lines. Moving around in Blender's viewport is a breeze, and silky smooth; it's like going from watching videos in 10/15fps to 30/40fps.
The only slight downsides are that it seems that sometimes I haven't quite mastered its acceleration tendencies, meaning that trying to hit targets in menus is still a bit clumsy (though what can you expect, having only used it for an hour or so at this point), and that while the scroll-wheel does make click-by-click scrollwheel usage nice and distinct, for scrolling webpages it currently still feels a little bit on the stiff side (but probably not more than the basic HP mice we've got in the undergrad labs in the department this year).
EDIT (23/6/2014 4pm): I've just learned this afternoon that the buttons on the side do get picked up by Dexpot, and that it uses them for switching between workspaces...