Well I just got back from the prerelease today and feel that playing with this set I learned a lot about it. This is not a tournament report, I'd just like to share my thoughts.
1. Student of Warfare lives up to her hype. This card is the closest to it's inspiration, Figure of Destiny IMO. It's a very hard card to come back from in the early game and hits hard and levels fast. Only one person at my release pulled one and used it but the games he won were mostly decided by the little level upper. The one game I won against him and the one that I drew were because I was able to keep the student off the field or blocked.
2. I don't think level up is good for Standard but it's better than it looks on paper. The issue of tempo with Level up is odd. There were several times where leveling up the creature was the best possible move and I couldn't immediately think of a situation that would be too different from the standard scenarios I've had described to me where the cases wouldn't be similar. The reason I dislike the levelers for standard is they're even more devastating to get killed than normal creatures.
3. Black and White seem to have the best levelers interestingly IMO. Black has a leveler that becomes a 4/2 on turn three as well as a new vampire that will likely be too big to stop with Deathtouch very early. White's levelers are all pretty reliable and some come in with decent stats even before levels.
4. The Eldrazi are annoying but not unstoppable. They're really rather obnoxious cards but Control and aggro decks are gonna have ways around these brutes. Most of the ones I saw were cast off the backs of some heavy Spawn Tokens. This leads into....
5. Kill those tokens! (and tiny creatures that are getting in the way) It's a bit odd but based on the way Wizards described it, it sounded like you would be saving your removal for big creatures mostly. Yet I found myself saving myself more often from death by handling the smaller, more efficient armies quickly. It still doesn't hurt to leave mana open for a spot removal deal.
6. I expect a black variant of spreading seas to pop up and or a Vampire control build to be viable. One of the games I lost excruciatingly was to a red/black deck that was designed like Spreading Seas. It controlled my land and burned away my creatures as well as discarding them while he built up to the Eldrazi. I don't see why this couldn't turn into a viable strategy outside of sealed. Plus that new blood chief is ridiculous.
6. Jund colors aren't really going anywhere. I saw G/R, G/B, and G/R/B quite a bit at my release. This just confirms what I'd been guessing at, and that Green is going to be heavily favored followed closely by black and red. Naya colors saw some play as well but Jund's colors seemed to lead. If this trend continues and carries over to draft, you may want to stay out of those colors in draft.
7. It's still too early to call it on Deprive IMO and Blue in general right now. Blue is definitely not as strong this set as the other colors but I think it is being undervalued right now. Only a couple of people I saw were playing it and none of them more than a bit. Again, this could prove useful in draft.
8. Rise definitely has weaker removal. Stuff like Oust and Regress can't really compare with Terminate and Path. On the bright side, we do get Flame Slash.
Well that's all I can think of off the top of my head. It's spinning a bit at the moment and I admit, I'm tired. If you learned something interesting at your prerelease please post it here. I'd love to hear it.