I have a Konica C3080 we picked up a year ago, and have run Konica C1060s prior to that. They have been reliable and print quality has always been excellent. I haven't run Xerox, but I have heard stories about them being more problematic (as well as Canon color machines), but as I don't run those. I'm sure there are an equal number of people who will praise Canon or Xerox.
Others are right - service is absolutely something to think about. I've had people offer me great deals on other equipment, but their service is coming from 2 hours away. Even with a 'guaranteed' response time, I don't want to hear "Well we need a part, we'll schedule to come back". My techs and their warehouse are 20 minutes away and they have techs dedicated just to production-grade equipment; that's valuable.
Regarding the C3080, jams are very few and far between and it's handled just about every type of stock I can throw at it. I think all of the manufacturers have some sort of in-line calibration available - Konica has had spectrophotometers inside their relay units for a while. Now
Konica has the 'IQ-501' unit - I have this on my press. Personally, I wouldn't want to go back to running without it. Exacting color and front/back registration, continuous monitoring during print runs, easy creation of output profiles, engine and controller calibration...it's great. I run an in-plant, so most of the work we print has our brand colors on it, one of them a custom spot that's kind of a pain to hit. Both our marketing department and myself have never been happier with what's coming off the press.