I was finally able to beat the Mithalas god, I got the beast form, got the spirit form, got the pirana pet from the frogman, went up until I reached the sun temple god (that worm thing you encounter after the the path filled with spikes, with the water going up and down). At this point I got stuck, went totally frustrated, started to hate the game and deinstalled the whole thing.

Now, I still think Aquaria is a great game, with brillant ideas in gameplay, and a wonderful athmosphere... But to me it had some big flaws, that made me hate it in several points, and I would like to explain why.
First, though, I must admit that there is one thing I have always hated in any game: having to jump from floating platforms and avoiding spikes. I know there is people who love this, but I just can't bear it, and that is probably responsible at least for 50% of my disappointment with the game. On the other hand, one thing I have always loved, are adventure games where you have to solve puzzles and riddles, but on that side, in my humble opinion, the game lacks in communication with the player. The game is full of hints, but most of them are kind of hard to decode, and a lot are really hidden, or too far fetched to be understood, and generally speaking, the game is really vague on what you're supposed to do.
You know, there is no game without rules, every game has rules, that define how you're supposed to reach the final goal. These rules, in Aquaria, where never really clear.
Most of the problems with the game reach the surface when you have to face a boss. A good example is the Mythalas God: how was I supposed to know that shooting at it wasn't doing any good? The rule to beat the boss is: throw poison frogs in his mouth until he turns red, then shoot him. But then again, how was I supposed to know I could shoot him when he was red, since I couldn't do it before.
The first time I confronted the beast I spent 30 minutes shooting it, until I started to think that either the energy of the beast must have been 7000 hp or it was immune to my shots. The problem was that there where no real clues (like a sound of some kind or a visual clue) that made me understand it, so you had to try a lot to find out. Once I got this, I had to understand that the poison frog was the solution, and actually I was already bugged enough, so that I went to the forum to seek advice, because I hardly have the time to try... you die and die again and just get frustrated a lot. And this is mainly because the nearest save spot is 3 levels above, so each time the beast kills you, you have to do all that swimming and dodging creatures down the stream, over and over again. Somebody told me there was a save spot right there, and in fact there was one, unfortunately you had to kill the boss before you could reach it, since it's right there behind him. The same person that told me about the save spot said that I would have understood if I had read the Mythalan writings on the wall... hmm... well, that's a great thing if those writings actually make sense, and are not simply a decoration of the background. I would never have thought that they could make sense in the first place, and it really shouldn't be something you must know to be able to progress in the game.
There's spots where the communication works better, like where you have to get the gears spinning, the game gives you a clear hint, and then you just have to figure out what to do with the hint.
Where the frustration reaches it's peak is, for my personal experience, the part where you must battle the sun temple boss. The boss itself is quite a challenge and you have to try a lot of times to find out what's the best way to kill it. The fact that you have to jump over those spikes just to be killed by that beast, over and over again, just got me completely mad.
The problem here is that the controls are not very accurate, so you end up hitting those spikes a lot of time, reaching the monster with little energy left, so you have even less time to try things.
It might be me who's a bit impaired o these kind of things... but then, I might not be the only one...
All in all, I loved Aquaria from the first videos I saw... but now I'm just too frustrated to play with it... anyway, I'm not telling you this because I need to complain with somebody, I just want to express my critique on the parts of the game that could be better, because I see the huge potential!
Hannes