Far and away, and the greatest innovation, is First Person mode as far as what I like best.
At fist, I did not use it until the last levels, with the judas. You can use the hotkey for treachery attack in third person view but its sooooo much more fun in FP. Then other levels, like REclamation of Talonthia, became more fun with FP. PS, just beat this level with NO SAVES bwa hahaha.
Any of you "kids" here remember the gaming landscape in 1998/99? there was the tombraider series, which also had a FP view, but only when your avatar was static. That's why lara always auto-aimed her guns, a merciful addition by the designers.
Just look at game like half life, another contemporary... blood, blood and more blood. I think I rememver reading somewhere (was it in the manual?) that Acclaim's designers wanted a hard core battle game without all the blood, hence Machines. Another great point.
NO CHEATS built in to the game! I was hammered by Behind Enemy Lines for over a month, no kidding. What a challenge.... another pro.
The "tab" key to select special weapons in first person ROCKS.
The battle effects are indeed spectacular, ground punch, plasma weapons, and that insane sound the Goliath makes when firing

... not to mention the Eradicator! When your tooling around in FP and you hear that crazy Vortex weapon go off, you KNOW you're in deep s**t.... superb.
Only one "con" and everyone agrees. The AI. It's tough to deal with the hesitant movements of groups of units. It's like theyre all figuring out how to get to the same empty spot, then realizing it isnt empty (because 10 other units are on thier way to it too) it has to decide where to go. Forming squads with commanders seems to help, I will test further and report back
