Okay, so I must say it didn't work for me, but it might be my fault. Seems like it stopped installing because I didn't have enough of free storage and now that I have deleted some things, I think that the drive shows 2GB less in total.
Well, "just". I wouldn't ever complain over such thing, go and create what you want. It might even bring more users back to the community, so it's a win anyway.
Except that you can play more games online on 5.5.1 and 5.5.1 is apparently more stable, so you won't have a way of updating to it once a newer firmware is released.