Hey Sky, Mike has answered a lot of questions but you asked about why the Ultimate wouldn't be a good pattern plane and why pattern planes fly straight.

1) The Ultimate is soooo short coupled that it is by design, not smooth in its movements. I've had several and this is the reason. Couple that with many 3D pilots have their throws simply too high or too much surface movemtent. Not a bad thing but contrary to flying smoothly and making multiple extremely small adjustments to ail, elev or rudder to fly straight or wings level. If you can add a ton of expo, and dial the rates down to a minimum, the Ultimate will fly well, but at these rates wouldn't 3D well.

2) Pattern planes don't fly any straighter or handle the wind any better than other planes!!!!! Wind still effects them and poor piloting still effects them. Watch a pattern pilot land on a crosswind day, and he has that plane crabbed all the way down to 2 inches high then adjusts the rudder to touch down.
Flying straight, consistant, smooth radius', same sized loops, wings level all comes from 2 things, Practice, Practice practice and a will to accomplish flying in this manner. As Mike said, boring to watch, but when you're trying to make the plane fly a specific course, one day wind in your face, the next day wind at your back 10 mph, next day down the runway 20mph(you get the idea) the boring is off it pretty well. I still after a number of years enjoy trying to fly a specific smooth prescribed way.

At the TOC most of the pilots had an early start in Pattern and their freestyle routines, although with lots of 3D, were always in control. When I first learned to do a snap I had no way knowing which direction or orientation the plane was in until after the snap, as an example. These guys have total control as Mike said, because of the basics learned.

Good luck.

ed