I switched to a non-jet valve head 10yrs and 30k miles ago and have no complaints. There's been no loss of performance or decrease in mileage and that's with the Mikuni carb. Compression improved from 165-175 to 180 all around. Emissions increased slightly, but they were still well below the legal limits.
There may be quality differences between heads of different manufacture (I recall those cast in India were crap), but as a rule, the switch shouldn't diminish performance. Take a look at Engine Machine Service, Inc. in Niles Ohio. They've been catering to the starion/conquest crowd for years and they sell only non-jet valve heads.