Mechwarrior 3 was one of the better ones in the series. The only two minor complaints I had at all with it, were that there were like 17 rounds of gauss rifle ammo in the entire game with ammo being a separate drop from weapons which was a problem, and that you had to escort your C&C repair trucks, and if you lost one you may as well reload. That and the two annihilators you fight.
...Yeah. That's pretty much the entire list of negatives. Otherwise, it was a huge improvement over MW2, and still followed the actual battletech mechanics and stats, so it never really got a proper sequel. As much as I like MW4 mercs, it's a totally different game that doesn't stick to the source material like MW3 does.
I particularly loved how the pulse lasers in 3 were steady beam lasers you had to hold on a target, so they played very differently from the normal/extended range lasers.
Every once in a while I want to play MW3 again, and am reminded unfortunately that it really doesn't like modern hardware, and even in the best case scenarios when I can get it to work, it almost never is with recognition of modern flightsticks. If we could get a GOG version that runs on modern systems and works with flightsticks again, I would buy this sooooo hard. This is a "shut up and take my money!" scenario.