Thunder Game Works' Trenches was quite the hit on the iPhone last year, combining a cartoony World War 2 setting with some solid real-time strategy combat and quite a few innovative game features. The game also spawned a few spinoffs, and was popular enough for EA to publish the sequel.
There are some new features here. There are new unit types such as Cavalry and Snipers to hire and deploy for your armies, and the single-player campaign is significantly more fleshed-out, with an actual campaign to run, complete with choices to make about where and when to attack. But more or less, the action is pretty much the same as the first title, with you recruiting troops by earning points and then moving them around the battlefield in real-time. If you liked Trenches, you'll probably like this, and if you didn't like Trenches for whatever reason (the troops can sometimes be a little hard to control, and the strategy isn't always super deep), this probably won't win you over.
In fact, the differences might send you back to the original game. EA has implemented a "perk points" system that works like a freemium title, where you can buy more for convenience, or sign up on EA's Origin game login service for extra points. Some players might not appreciate that. The iTunes reviews also say there are some issues with crashing, though I never had any on my iPad 2. That might be more of an issue on older devices.
All in all, Trenches 2 is more iterative than innovative. It features much of the same gameplay of the old game, though there is some new wrapping around that fun. If you liked the old title, you'll probably enjoy this one a lot, and at a price of 99 cents on both the iPhone and the iPad right now, Trenches 2 is worth a try if the idea of a real-time strategy battle appeals.