To be honest, I really didn't like it all that much. As has been said before, you DO have the potential to develop this into a real piece. Actually, it reminds me of the compositional style of one of my friends- he can't complete any single piece effectively because of dead-ends and momentary whims. Although there is a single theme running through this piece, it still seems VERY fragmentary and not as well-connected as it has the potential to be.
As for the repetitions...well, like Danny said, it's vey important to have them, but I got a little tired of it coming back EVERY SINGLE time in the same key, and never seeming to develop properly, or build any tension. Although, it is worth mentioning that at 4:45 you started to go somewhere with it in the major, repeating the theme a few times in different harmonies, but then it succumbed back into tedious repetition in F minor.
Although you may not have improvised it, this most certainly has more of the feeling of a gigantic Impromptu than a Sonata, per se. I strongly advise re-thinking the process in which the piece develops.
Phil