Echo Prime was originally an iOS action RPG, and it shows, having very simple controls. Worse yet, the controls in the PC version really don't work that well - sometimes clicking anywhere near an enemy will shoot at it, even if it's already dead. Also, your dodge roll behaves erratically and buggily, often not really moving you the way you want it to move, or at all.
Likewise, it shows its iOS roots by having a lot of very simple, repetitive levels. It took me about 10 hours to complete the campaign (at least through hitting level 33 out of 50 and getting the final campaign achievement, End of the Line), but most of this was essentially just grinding the same kind of missions I'd already completed a dozen times over. Further, it's not a loot-fest at all - basically you just get to pick one of three or so items for each slot from the store each time you hit a new tier of 5 levels.
The Echoes do look amusing and provide for on-the-fly character customization for each level, and some of the boss fights are amusing when the controls aren't actively getting in your way of completing them, but all in all I can't really recommend this game at any price. It's just not fun.
Sorry, Robot Entertainment. Your other stuff's all good, so maybe try again!