What did you open up at the Prerelease? How was the set?
Dragons of Tarkiir is an interesting set. I did the Iron Man challenge at our local store (that's where you play in 6 prerelease events in a row over the course of the weekend), and did 3 events with Ojutai seeded prerelease pulls and 3 events with Silumgar. As far as first impressions go: the new clans seem to be pretty balanced with no real leader. The new mechanics are all really solid, but if I had to rank them in terms of limited play impact I'd say that
Dash is the most impacting with
Exploit coming in at a close second.
Rebound is as solid as it has ever been, but I feel it will be more relevant in Standard than Limited.
Bolster is -much- improved over its first iteration in the block with many fair-bodied creatures having not only
bolster 1 but
bolster 2 and
bolster 3 as well. Lastly,
Formidable is really impressive and very easy to get active in Atarka R/G. I don't think it will have a big impact on Standard, but in Limited it's solid.
Dash is incredible in Limited because a large portion of the control/removal is sorcery speed and
Dash makes it so your stuff won't stick around long enough to get nixxed. Also, there are a few creatures that actively boost the offense of
Dashed creatures or reduce
Dash costs.
Exploit is easy to abuse with the right pulls due to a sort of slow synergy of casting creatures with ETB effects, sacrificing them to trigger
Exploit ETB effects, then bringing them back to your hand with 'When this creature dies' effects. It's a very solid synergy with a lot of cards to support it.
As for my pulls: my buddy in two-headed giant opened a Narset, which was awesome. I opened a Silumgar, 4 Silumgar Commands, and a few lesser rares. No bombs or money cards, though. No Sarkaan or Narset. The set is quite large, but to be honest the two planeswalkers are likely the only really big money cards at least until Standard adapts. I expect Secure the Wastes to be a big one, though, and the new Megamorph Eternal Witness.