I like the gameplay in this game and the level-creator is differently well realized. 
It's pretty easy to make a meaningful level in the creator - which actually make it so much frustrating that sharing levels is "broken". 

- There is no way to "favorite" levels you find... or users for that matter. It makes it hard to replay a particular level you liked again.
- You can't "browse" levels according to tags or something like that. 
- You can only vote for users and not level. Seems dumb because a truly good level-designer can actually only get one vote per PSN-user, regardless of the amount of great levels he has made.
- You have to vote for the user while playing a level... and can not do so after you've played the level. I personally tend to be focused on completing the level while playing - and forget to vote. 
- You can only "browse" levels by "highest ranking", "friends" and "latest users" (which might mean latest users playing or latest users who have created something... who knows). I don't have friends which play this game, and I can't imagine the "highest ranking" list changing much since people are more likely to be voting for them.
- You don't have any stats presented on your own levels. You can't find out if any people are playing the levels you've made at all. 
 
I really think it's a shame, because the creator in this game IS really easy to use and you can easily make something really good. For all the hype a game like Little Big Planet got for user-created content, it's really far easier to make anything complex in this game... 
 
I may come of as a little "ranty" and I DO enjoy this game... These things just annoy me because it seems like failed potential.