Unfortunately for this game, the original was better and what's new here does more to hamper the game than improve it.
The frustrating thing is that everything they have done new here isn't an improvement. The game is way harder, but not in that fun, challenging way. It just throws more enemies on screen at once and the first time you get killed by something off-screen, you will know my pain. The game is WAY too dark in some of the later levels, even when I jack up the brightness and contrast on my HDTV. The new weapon still doesn't make you want to go away from the trusty chaingun or flak cannon. In fact, it makes no sense to use since it's weaker than the standard weapons. The new vehicles are all terrible and aren't as good as your normal vehicle. The game is longer, which I liked at first, but the game seemed to drag on towards the end as the boring levels and lack of improvements from the original seem to be more apparent. And for some reason, the camera is pulled back farther in this game making it harder to see those tiny units. Even the achievements take a big step backwards here. Most of them are for the co-op game, are too hard or not fun, and you even get stuck with a 'collect every flag' achievement in the single-player. Ugh.
While I obviously have some issues with this game, it is still fun to play. It plays a lot like the first game and if you are into these dual-stick shooters, you might get into this game. It looks nice and the presentation is very good for an Xbox Live Arcade game. In particular, I really liked the music as the title screen theme has been in my head for hours. I was just expecting more from the game and, at a minimum, I was expecting that the new "improvements" would actually be beneficial to the game. So if you loved the last game I would definitely check the trial version of this game out. If you haven't played the first game, I would go grab that game instead. It's cheaper and better than this sequel.