I liked it for the most part.
Letters I liked: (11/26)
A - for awesome. It's fun to make them do the wave.
F - I like the falling and interlocking effect. That was good.
I - Love it. The dots become soccer balls and create great group effects.
J - Bye, bye, birdie! One of the more enjoyable effects.
K - Great explosion/reassembly effect. Again, really cool to view using group effects.
L - This is not impressive on its own, but the slinky effect it creates using the first group effect brings back memories of my Slinky...
O - Cheerios. The one and only. This was one of the best in my opinion.
R - Whee! Trippy multiple image effect! I love the chaos which ensues in the fourth effect.
W - for WHEE! Love how the second effect seems to emulate a strand of DNA.
X - I liked this one for the same reason as K (explosion/reassembly)
Z - This was probably my favorite effect. It's fitting that you would save this for last.
Letters I thought were okay: (13/26)
B - Sure they turn and rocket off, but it doesn't work so well in a group.
C - I don't quite get what you loved so much about this effect.
E - Okay. They explode. The group effects are also a bit buggy.
H - Fireworks are alright, but not awesome.
M - More explosions? Not the most original idea.
N - Kind of weird. It could've been better.
P - Look at those mugs. Seriously, mugs?
Q - I've always wanted to crush a q... wait, no I haven't. Ah well.
T - I practically sneezed.
S - Animation was kind of long and too MS Paint-y.
U - Like S, only a little worse.
V - Again, the MS paint was a little bland.
Y - MS Paint.
Letters I really didn't like: (2/26)
D - was pretty lame. All the letters just temporarily vanish when a giant car barrels through.
G - made faces show up and played annoying sound effects. Group effect number 3 makes a disharmonious collective noise (to say the least).
Ultimately, less than half of the letters had an effect I liked; however, those letters were so enjoyable to play with that I feel you should get bonus points for them. Also, offering 3 different tracks to listen to was a great idea (and a mute button, in case you hate every track).
Crunk fo' shizzle.