I also just picked up an Evolve 4 at Petco just this afternoon. I hadn't planned on getting another tank for probably a couple of months at least but considering the $34.99 price tag and the fact that it was the only one left, just couldn't pass it up lol. Super excited to plan out which plants will go in it and the aquascaping. Right after Petco I made a quick stop at Petsmart, where I saw that their Evolves were also on sale, the Evolve 4 for $59.99, so still significantly higher than Petco.
I think I've already scratched the idea of housing one of my bettas in it--judging by several of the posts in this thread it sounds like the filter flow is pretty strong, and while baffling/modifying strong outflow can be done pretty easily, I'm not sure even that would be sufficient if the pump is that strong, plus the water level has to be quite high due to the placement of the intake slots so I'd have to make my own lid to prevent any suicidal jumps, which I really would rather not do. I could definitely end up changing my mind though once I get a better feel for the tank lol.
Really like the idea of making it into a planted shrimp tank right now, but theres no rush to decide. This style of tank also lends itself quite well to conversion into a nano-reef tank (with certain modifications of course), which I'd really love to try since I just started dabbling in SW and am really enjoying it so far. Tempted to check out the other Petcos in my area to see if they still have any left and get a 2nd one lol.