I dunno, Signa. My teacher (and my experience) says that much time can be spent rushing through a section again and again rather than learning it slowly and correctly from the get-go. My teacher says that (for recital preparation) playing slow is like putting money in the bank. Playing fast is like making a withdrawal!
I would think that trying to play fast while still learning would just reinforce mistakes via muscle memory. Also, I have found that if I play slowly during practice, I can fire the piece off at a wicked tempo without ever practicing it fast.
When I'm learning a new piece (like I am right now!), I do the following:
1. Start slowly (either from the beginning or from the end, as I described above), hands together. (The hands together part, I hope, might help with sight reading).
2. Once it is starting to come together, gradually increase the tempo. Take each troublespot and use an excruciatingly slow metronome speed, dialing it up as you get better until the trouble spot is no longer a trouble spot.
3. Add dynamics and phrasing.
4. Add pedal.
By this point, I'll have no need to work on memory, except maybe to play it a few times hands separate, just to double-check my mastery.
This process, as you might imagine, is quite painful!