Early ones had an issue in hot weather with the MC jamming up due to close tolerances. Not something I ever experienced.
I took the bike out for the first time with my new V4s fitted at the weekend. To sum up, they’re like RSCs, but just a bit ‘more’ of everything -power and modulation. The feel is very similar though.
If I hadn’t had clearance issues with the top tube I wouldn’t have sold my Guides. The V4s are very, very good, but more finicky with setup. And a lot more expensive. They are, however, incredibly easy to bleed, especially if you’ve got a Mityvac!
Only complaint I’ve got is they do sing a bit on first application after periods of non use in the wet, which my Guides never did.