I personally don't think Vortex is that bad. It's a 17 year old steel coaster (and an Arrow one at that) so you have to expect it to be a little bumpy. I think it has aged much better than some of its' counterparts, mainly due to the excellent job of PKI's maintenance department. Could it use the new-style Arrow trains - probably, and that would help a little. But I don't think that would fix the problem. As with most other Arrow loopers, it seems to be that the transitions are the issue - there are definitely several points on the ride where you feel the train "jolt" (someone mentioned the turnaround before the first vertical loop).
I agree with Sparky - the ride can be very enjoyable if you ride defensively and anticipate where your head needs to go next. I'm 6'1" and while that keeps the majority of my head above the OTSR, I can still get a swift hit to the jaw if I'm not paying attention. There are so many unique qualities about Vortex however (the first drop when sitting in the back car, the sheer height of the corkscrew, the boomerang element down in the "ravine") that make it well worth it for me.
Give me Vortex over some of those other steel loopers (Viper at SFMM, Manhattan Express in Vegas, etc...) any day of the week!