I couldn't really understand why Jim Carrey's character decided to have his memories erased as well - it seemed pretty random to me, he had no reason other than "she did the same and she's with another guy now, so I'm unhappy and I want that to go away".

I haven't been promised a philosophical film. Have you seen the trailer?
First, there's the supernatural component, presented in a comedic fashion. Then, they show a lot of happy scenes, mixed with some of the weird stuff and happy music. So of course I expected a "rom-com with a supernatural twist".

The problem is the visualization. It's a beautiful movie alright. But from my p.o.v., the illustration didn't help bring the point across, it more so distracted from it and utterly confused me as a viewer. The "frame story" arrangement didn't help either. They shouldn't have done that if the movie wasn't supposed to be a mindfuck à la David Lynch.

Also, I didn't like Kate Winslet's hair at all, it's yucky. ;)