Summary
Entertaining with a few asterisks
The Good
WWII GI's creators had lots of good ideas for missions/levels, including the "Saving Private Ryan" take-off, which is very challenging.
It's nice to be able to seize enemy weapons, a feature which was not present in WWII GI's predecessor, Napalm. Also, the graphics are much better than Napalm.
The Bad
Weapons in WWII GI are lagging. Unlike its predecessor Napalm, which had 10 clearly differentiated weapons with different levels of effectiveness in different scenarios, WWII GI has lots of overlapping weapons (for instance, the Thompson submachinegun and MP40, which have almost the same capabilities; the BAR and sniper rifle, which serve similar purposes; and the TNT and explosives, which are identical as far as I can tell) as well as ineffective weapons -- aren't Bazookas supposed to be able to destroy enemy tanks?
The grenades are also a problem, you can't throw them that far and they don't seem to destroy Nazis 50% of the time, even if one detonates right next to an enemy soldier.
AI is useless. Fellow US soldiers randomly fire shots in a certain direction, even if you have to go in that direction -- this makes getting past the first level, D-Day, extremely tough as you are constantly riddled by bullets from other GIs as you run up the beach!
The Bottom Line
Fun way to kill a couple of hours, but this is no Half-Life.