This is a game from the creators of Revenge Of The Titans, a top-down shooter at it's core and so much more once you get into the depths. Each bot you can control has a generally unique description and use, some are good at tanking, others good at firing missles from a distance. This game encourages exploration and essentially is a score attacker's wet dream.
Breaking down the mechanics, you can control up to 8 different units at a time, although doing so is risky. Once you release control of a certain droid, you've handed it over to the AI which isn't entirely tantamount to suicide for the bot, but damn near close. Either way, you'll be doing most of the work unless you simply don't want to. There's a variety of playstyles that Droid Assault caters to, from the sniper to the tank, and better yet.
There's upgrades. Not all upgrades apply to all bots, but the vast majority do. Speed, defense, attack damage, armor. Powerups litter the field and the game pushes you do pop open every single crate for that either special overleveled bot, or a weaker variant that might just drop that piece of salvation you've been looking for. Crates themselves serve as holding containers for random bots geared towards the level you're playing on. So you won't be getting a massive boss-esque bot out of one in your first level or two.
Moving onto Bosses, there are a slew of them in the game that all follow the same archetype. Two to four guns on each side which are destroyable for further powerups, and a primary weapon. Tactics mean everything or nothing depending on how well you've progressed. There's a defenite rougelite element to the game and it's worth replaying over and over if only to get that final ending.
Basically, buy it. It's good, fun, and a new update just included local co-op which supports the gamepad wonderfully. You wont regret it unless you've forgotten there's a demo out as well: http://www.moddb.com/games/droid-assault/downloads/droid-assault-demo