1. SFIV has retard-tastic Shoryuken shortcuts because apparently this was one of the most difficult motions to perform by n00bs and Capcom wanted to make SF more accessible - the shortcut is df, df instead of the usual zig-zag f, d, df and makes certain charge characters perform some other attacks instead of the move (especially the Dictator - Neurosis, one of Japan's leading Bison players did this TWICE in a recent match

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Yeah... I recognized that... Shoryuken are much easier than in SFII. Had always some problems back on SNES.
2. The timing on the Ultra is slightly different than on normal special moves. In normal special moves you press the attack button precisely at the end of the motion while with the Ultra you should press it slightly AFTER performing the required motion.
I'll try to look for this.
Having said that, charge character combos of the b(2), f, b, f kind are best performed with db (the pro way of holding charges), f, b, UF - this makes sure you're not hitting any of the "down" diagonals. After teaching myself to do the combos that way it fires off pretty much each and every time.
I'm doing charges with db since I got SFII on my SNES... so that's not the problem, but I'll try it with uf.
When it comes to Guile's Ultra I saw a good tutorial on Youtube which I sadly can't find anymore. In it two methods of inputting the motion were shown. ^^
Update: I found it!
YouTube video
Ok... that looks fucking easy in the vid...

... especially with the nice klack-klack-stick.
