I watched the GP Seville from start to finish and the SCG Houston Open this last weekend. The four main deck types were :
U/B Control
R-W / Jeskai tokens/aggro
G/R Devotion
Abzan aggro/midrange
Yeah there can be massive changes in those deck 'archetypes' with relatively few changes, so please don't pull me up on that.
Top 8 deck lists in Seville were very different from the top 8 in Houston, which was also true of most entrants. The US Open top 8 was largely R/G and R/W, neither of which decks made the top 8 in Seville. Standard of play wasn't top notch at either.
Top 8 in Houston :
=1&start_date=2015-02-14&end_date=2015-02-14&state=TX&city=Houston&order_1=finish&limit=8&t_num=1&action=Show+Decks]Magic Deck Search Result!
Top 8 Seville :
Top 8 Decklists | MAGIC: THE GATHERING
Things to note : I believe control now has the tools to be a tier one deck and possibly the top deck. But it needs good players and not just good players but good players who can play at pace when needed. I'm very much looking forward to seeing what Ivan Floch plays this weekend in Miama - he's excellent at control and at putting control decks together. Expect him to run one or two Ugins and some Crux of Fate. He might even use Ashiok or Silmgar or Tasigur, though he is usually conservative.
G/R was running an extremely fast ramp to put out up to 40 point 'fireball' Craters Claws quite early in the game. They run 3 or 4 Nykthos as having one in play and playing one is actually good for their 'fireball' strat. They also run Whisperwood Elementals as wincons. I expect this deck to see a lot of play over the next couple of weeks but I also expect to see it fall by the wayside. It's got the same weaknesses as Ross Merriams G/B Constellation deck from last year - counter some of their early dorks and they really struggle to get devotion and mana going from turns 3 to 6. One note on this is that Nissa is strong against Ugin with the forest creatures being colorless and some were also running Ugin to counter R/W and token decks.
R/W not much to say. It was strong last year and it got a boost from FTF. Most players went with one or two Soulfire Grand Master along with 3 or 4 Seeker of the Way. Most decks didn't use Monastery Mentor, though the losing finalist in Houston ran 4. Hordeling Outburst looked strong in a lot of matches.
Abzan I actually like aggro, but running 4 Rakshasa Deathdealers and 3-4 Anafenza, curving turn two Deathdealer into turn 3 Anafenza and turn four Siege Rhino. A lot were also running Fleecemane Lion with Thoughtseize as their only 1 cmc.
This weekend will see a higher standard of play so a lot of take aways from last week might go out of the window. Overall I think U/B has the tools to beat them all, but it's a very hard deck to play and it might take a little time for Floch to formulate the best deck. R/G is very strong but early disruption is hard for it to recover from. R/W tokens is as strong as it was. Abzan aggro with the Rakshasas and Anafenzas is very strong if the draw goes their way.
Lastly, just a note that Tasigur and Ugin both live up to their hype and are very strong. If your deck can run them don't hesitate to include them.