I didn't like it as much as most people...
I like the tactical combat of this game. The sector management and conquest isn't very sophisticated, but it does make the game a lot more interesting than a linear tactical RPG where you can't pick your battles and territories.
I think the most exciting part is choosing and managing your mercs. They're all very well-defined both in stats and personality. They often make remarks that breathe so much life into each mission.
The BadThe game lacks the character-building/leveling elements of most RPG games.
To me, the appeal of most RPG games comes from taking weak characters and making them strong. This is just a personal preference and my review is very personal. Don't expect to do this in this game. The characters progress way too slowly to make them worthwhile in a long run.
You can't expect to hire a bunch of weak level 1 mercs and level them up to a point where they surpass the more expensive mercs that you can hire later on in the game. Their skills develop far too slowly, whether in the field or with dedicated time spent for training. If you end up getting a pathetic character to a high level, he/she will still be pretty pathetic and won't even be close to the other high level characters you can hire to replace them. The characters are meant to be disposable. You're going to want them to be killed off or fired in the late game to replace them with better mercs.
This need to replace characters is the one thing that really turns me off about this game. I want to have a band of mercs that I want to build up myself. It's been forever since I beat the game, but the only unit I remember keeping from beginning to end was Ivan, who was supernaturally good for a level 2 character anyway.
Aside from this, the tactical combat suffers because of extremely poor firing accuracy. The battles are unnecessarily long and tedious and very random because of how easy it is to miss. Even with a merc with 90+ firing accuracy, it's a pretty special feeling just to get in a hit from medium range because the overall firing accuracy is so horrible. Terrain and cover doesn't do much for the game either because when you're behind cover, you just seem to have as much chance of your shot not going through the tree or whatever you're behind as the enemy does of hitting the tree instead of you, so your own cover ends up getting in your way. The kneel feature could have been really useful but it wasn't put to use the way it should have been.
The maps are also far too big. If you think X-Com is annoying when you are down to one hidden unit on a map that takes 30 turns to find, just wait till you see Jagged Alliance. I've spent an entire day (in game time, not real time - maybe 20-30 minutes of actual time in reality) searching for a single unit. They move around like crazy and with your small party it can be a nightmare to spot the last enemy. Mobilizing your force across the map in turn-based time is also a major management pain. It makes you want to sacrifice strategy and have the most agile guy just move ahead of everyone and dispatch the enemies just out of laziness.
The Bottom Line
This is a pretty fun game if you like tactical RPGs. I just don't agree with other people though who think it's as good or better than X-Com mainly because of the lack of character building (X-com not only has this but also combines a far more sophisticated management game) and the less sophisticated and far more tedious tactical combat.