Ive heard some reviews saying it has wobble in the headset. Is it bad wobble? If so, can I fix it?
The RUP is a Threaded headset compression system and those are just inherently prone to being loose and since they are produced on such a large amount not much is done at the factory to make them "Dialed" and they don't pack much grease in the bearings either.
As Dom mentioned you'll need to tighten up the system to make it run a little better.
Kind of a pain to tighten up unless you have the thin headset wrenches.
First you need to remove the Top locknut, just take it all the way off. Then remove the Threaded Top race. Remove the bearings and put some more Bearing grease in there.
Put the bearings back in and replace the the Threaded Top race and tighten so that the Forks barely spin, you don't want them too loose.
Install the Lock nut and tighten it- this is where it is a pain because normal wrenches are too thick to grab the Threaded Top race nut and hold it while you tighten the top lock nut. (If you have a Local bike shop they may have the Thin wrenches and would be worth the trip to the bike shop.)
Put the bars on and make sure the Bars and bar clamp is all the way down touching the Lock nut- this will help keep the Lock nut from loosening. I've adjusted a lot of RUPS at the skate park where the kids do not have the bars all the way down.
Tighten the bar clamp.
That's about it but don't expect much from the RUP compression system- they build the RUP as cheap as they can BUT the deck it self is pretty good and a good way to get in to the sport since you can always change to a Threadless system.