There's 50 puzzles in all (fewer than Lemmings!) and most of them give you more than enough resources to easily solve the puzzle. You're not gonna be wringing your hands and soul searching about how many you can afford to sacrifice, because you have to save them all, but also because the puzzles are never going to ask that level of dedication. A big difference, is that you can plop down blocks or erase them manually, where Lemmings required you to designate a particular Lemming a digger or a builder, and hope he'd be able to do his job properly. It also means that time isn't as big a factor, because you can build anywhere on the map and get things set up before the slimes get near it.
One frustrating thing is that the slimes seem to choose a random direction to walk after a fall. 4 of your slimes will go right towards the exit, and the last one will go left towards spikes and his doom. It's a layer of artificial difficulty which makes some puzzles (I made a note of 38) either easier or harder than they oughta be. There's no room for random in a puzzle game, all variables should be as controlled as possible. Stranger still, using the red power-up on Slimes seems to occasionally spawn an extra slime. I only noticed this because my red slime would hit the ground and one would walk left and one would walk right. That also introduces an extra slime that the game isn't expecting, and the ability to "solve" the puzzle without all the slimes being there. I'd look into it.
There's another glitch that makes the game easier than it oughta be, where you can sometimes click to place a block or a chute/ladder somewhere that the game says you can't, but it gets placed anyway, blocking a fire or a monster and sidestepping that particular issue.
The game does a bad job of introducing you to the power-ups. Somewhere in game telling you what they do would be nice. Apparently red slimes are immune to knives, slimes who touch fire ignite and will dehydrate if they touch a barrel of oil. Blue slimes can revive these, but slimes who die via other methods "pop" and are unreturnable. That's actually one of the few good thins Spoonweaver's added: Some puzzles only give you one or two slimes, and require you to get to and revive dead slimes throughout the map before reaching the exit. Those were my favorites.
It's got virtually no replay value, not a whole lot of challenge and some bugs. It's worth your time, I think I finished in like an hour, but probably not worth a dollar. The comparison to Lemmings is inevitable, and if you can get your hands on a copy of Lemmings that's probably the better way to spend an afternoon.
PS: Why so tile based?
PPS: Why no fall damage?
EDIT: I'm sure someone will move this to the right place. Sorry!