1. As far as buttons go I'm pretty sure I'm going to go with the Happ horizontal pushbuttons.
Good choice
I'd be okay with clicky as long as it was smooth. If I'm playing Street Fighter and spinning it around I wouldn't want it being rigid or getting stuck in a "corner".
I don't play fighters, but from what I can gather - circular motions (Capcom???) are better on the Supers. Discrete diagonals (corners) (MK

) are better with Competitions. T-Sticks will have less travel than either one. You will probably either want a set of OSCAR's restrictors or a true 4-way stick (Omni-Stik or Euro-Stik) for 4-way classics if you play these.
3. Trackball. Thats $164 compared to $86. Is the Happ worth almost double the price?
Not to me.
I'm not sure where to go on this one, hopefully you guys can shed some light.
Sure - 2-1/4" - Ultimarc or
www.wicothesource.com - $28,
www.oscarcontrols.com USB mouse pre-hack - $12.50, total $40.5
3" -
www.wicothesource.com - $50.00,
www.oscarcontrols.com USB mouse pre-hack - $12.50, total $62.5
The opti-pac is nice if you want a spinner and a trackball on the panel, as they can both be hooked up and will auto-switch. In this case, it's a better option than two OSCAR hacks, b/c these may switch positions on re-boot, although this can be avoided by using hacks from different manufacturer's, using one hack with a DPDT switch to select between trackballs and spinners, etc.
4. I'm planning on going 4 players so I was going to get the ipac4.
Makes sense.
Thanks for any advice guys, and let me know if I'm forgetting things, like if the Happ buttons won't work on the ipac or something else that I wouldn't have thought of.
Only thing I saw was maybe a spinner or mouse buttons for the trackball, but you can do that with my recommendations.