I have use the OEM MC, a sleeved MC, and the CNW Brembo MC.
IMO, the sleeved MC is a noticeable improvement but it certainly does not provide "modern" braking or feel. In addition, the sleeving can fail - I had to have my sleeved MC resleeved again at one point. The Brembo MC (with stock caliper) makes the bike feel like a current machine brake-wise, great feel and stopping power. Obviously, the Brembo doesn't look anything like the original parts but CNW makes a plate that allows the Brembo to attach to the stock switchgear if that's any help.
This added a few minutes later: Frankly, my experience with sleeving was rather unpleasant due to the failure of the first sleeve after a few years - the brakes went from "normal" to the lever moving all the way back to the bar with no effect from one brake application to the next. Despite that, I had it resleeved but constantly worried about another failure until I bought the CNW unit.