Hey, nice subject to write on Steve !
Ok, since I don't have premium, I haven't read it, but according to the stats here
http://decklist.zmx.cc/ for the months of March first...
(number/cards)
1. 512 Force of Will
2. 480 Brainstorm
3. 395 Leyline of the Void
378 Polluted Delta297 Flooded Strand293 Underground Sea278 Island4. 242 Merchant Scroll
227 Wasteland5. 226 Duress
6. 171 Black Lotus
7. 165 Mana Drain
8. 163 Mox Sapphire
9. 160 Ponder
10. 159 Pithing Needle
So, for this month, it's FoW - Brainstorm - LotV - Scroll - Duress - Lotus - Drain - Sapphire - Ponder - Needle
Then, let's see for April :
1. 352 Force of Will
2. 345 Brainstorm
3. 288 Leyline of the Void
255 Polluted Delta232 Flooded Strand217 Underground Sea192 Island4. 187 Duress
5. 160 Merchant Scroll
128 Wasteland6. 125 Ponder
7. 125 Gush
8. 120 Thoughtseize
9. 115 Mana Drain
10. 114 Tormod's Crypt
We got Fow - Brainstorm - LotV again, then Duress - Scroll - Ponder - Gush - Thoughtseize - Mana Drain and Crypt. There is some kind of pattern here.
And for May :
1. 132 Leyline of the Void
2. 124 Force of Will
3. 124 Brainstorm
4. 103 Merchant Scroll
95 Polluted Delta81 Underground Sea5. 80 Gush
74 Flooded Strand6. 62 Duress
57 Island7. 56 Ponder
54 Tropical Island8. 52 Thoughtseize
9. 49 Red Elemental Blast
46 WastelandThe sample size is smaller, but we got : LotV - FoW - Brainstorm - Scroll - Gush - Duress - Ponder - Thoughtseize - ReB...
Based on theses recent results, one can safely say that FoW, Brainstorm, Gush, Scroll, Duress, are clearly the cards people play the most because Ubx decks are the bests (GaT, Flash, etc...)... Well, Painters may change that, but Vintage is a relatively stable format I think. Sure, these stats would be different if taken in mid-2005, but blue and black cards will always remain the top ones (or not :p).
This may not be the best spells in the game for all cases (besides that the sample size for May is really smal)l, but they shape the current metagame as they have shaped the past metagames too for FoW, Brainstorm, Duress, and alli.
My humble 2 cents... And I apologize for those bored by my lists.

EDIT : Link for the total stats (like since 2002, with a gap between somewhere 2003 and 2007, sorry for that) :
http://decklist.zmx.cc/decklist/card.php. Who's on top : FoW and Brainstorm, obv. !