Not everything's perfect in the indie world, sometimes you make a gem sometimes you don't. That's as natural as the mainstream. Gish was one of the first games that caught my attention because it was simple 2 dimensional platforming and looked pretty old school, it took me quite a while to get the game to play through because it didn't feel right. As of now I still think this game isn't all that great.
The fact you control a blop around trying to solve puzzles in a 2D environment might hand out some problems. For instance, controlling a blop shouldn't be easy, and the game make that point quite clear. Gish's controls are unwieldy, clumsy. It's actually hard to feel like you're in control since most of the times you're just praying for the game to register what you expected from what you performed.
Not all games that have this loosy control mechanics are bad at putting you in control, some are quite competent at it. For example, former Mario games didn't have that excessive momentum get gets these days, starting in New Super Mario Bros for the original DS, still the excessive slippery shoes of newer Mario don't break the game, it just makes less tight.
The concept of jumping could be implemented on the blop, instead they decided to add a little handicap. To jump in Gish the must must start bouncing, little by little storing energy with the blop's elasticity to reach higher heights. That's not too easy to perform, you take quite a few jumps to barely make a jump the height of Gish, and that would help much.
In the case of possibilities Gish can perform three different kind of maneuvers. The first one is what I call "rock mode", where Gish contracts and becomes heavier. If you're floating on water for example and want to steep in you can use this mode to do that. Attacking enemies should be performed with this stone mode as well, though it's tricky falling into their heads when it's so difficult to get altitude.
To execute attacks more properly you need to get a rather fast momentum, the stages don't allow much for that and most of the times the attacks will have to be thought ouver before advancing. The second form Gish can "transform" is slippery body. When used Gish is able to slip through smaller holes he wouldn't normally be able to go through.
The third and final form is perhaps one of the most important, with the lack of dynamism with the controls you'll find yourself using it a lot. It's the gripping Gish. When executed, Gish's body let out several filaments that attach him to walls and ceilings. It doesn't always work and seems to be a matter of choice from developers to make your path through a general route, and when it works it's not fine at all.
Not strangely if you think of it in a more objective sense, the filaments grasp the walls and the floor you're currently on, to detach from the floor and only navigate through the wall or ceiling you need to keep turning it on and off until it finally detaches completely from the floor and only on the wall. Doing it is extremely frustrating and often results in Gish falling off. Gish's movement are everything but intuitive.
I can't deny that if I was really controlling a blop in real life it wouldn't be easy and fair, but trying to overcome the loosy controls seems a pain and contrast with other games that offer completely tight controls. It's probably a matter of taste, however, some people probably feel satisfied with the slow-paced gameplay and grinding attempts. I can deal with grinding attempts, Super Meat Boy does it pretty well, but when the controls are against you it so easy to become frustrated.
The overall style is pretty nice, the levels are dark and there's even a very brief story going on, about Gish trying to rescue his girlfriend, though I doubt most people will even notice. The amount of levels is acceptable and there are levels to be downloaded designed by players around the world. If the single player didn't cut it for you the versus mode offers some extended play-time in a few different game modes.
One thing I can't seem to understand is why this game has a systems of lives. It's incredible that something reminiscent from Arcade times has survived for such a long time in a game that the player won't have any kind of loss from losing except trying again. It's unlikely someone would want to redo all levels again from losing all lives. The levels might be basic point A to point B, but sill, such an outdated system that doesn't have any place in the modern world of home console or PC.
If you somehow feel enthralled by it and want to fully complete Gish every level has its own share of secrets that will keep completionists busy. Overall Gish doesn't offer much more than a nice set of slow-paced aspects in a puzzle environment that requires patience to get the grip of. It might be worth giving a try if the player doesn't mind slow-paced games.