It's quite a bit late for the Spring one, but let us discuss our own (dis)satisfaction as well as expectations from the Spring season, and the current Summer season.
My personal Spring satisfaction list goes:
Spoiler
Saki
Phantom - Requiem for the Phantom
K-ON!
Higashi no Eden
Fullmetal Alchemist: Brotherhood
Hayate no Gotoku!!
Pandora Hearts
Hatsukoi Limited
Tayutama*
Tears to Tiara*
Asura Cryin'*
*Only other things I manged to keep watching, so not saying too much, just filling in the dead space. And yes, I'm serious about Saki being a satisfactory achievement. Eden's ending and some of the story development put it off for me, but it was pretty fantastic. Tight race for top 4.
This is my summer so far:
Spoiler
Bakemonogatari
Spice and Wolf II
Sora no Manimani
Taishou Yakyuu Musume
Kanamemo
Princess Lover!
CANAAN
Umineko no Naku Koro ni
Aoi Hana
Needless
Tokyo Magnitude 8.0
Yokuwakaru Gendaimahou
Umi Monogatari
GA: Geijutsuka Art Design Class
The Melancholy of Haruhi Suzumiya 2
Haruhi 2 obviously put to death with Endless Eight. GA bores me to sleep. Umi Monogatari is full of fabulous acrobatics I think.
Spice and Wolf II <33333 Horo. Sora no Manimani just has some wonderfully unique feel that's full of energy and entertainment. It feels like a whole episode of awesome is packed in each half. Taishou Yakyuu Musume, I had low expectations at first, but who knew watching moe girls try to play baseball would be so damn awesome? Kanamemo is full of adorable platypus. I just find Princess Lover! great. CANAAN develops too oddly to be put ahead of those, despite being awesome.
Bakemonogatari is the winner ahead by far though. Win can't even begin to describe how I feel about it.