Can't really talk about the roundwounds from Carvin, but I do like their flatwound sets, which I believe are made by LaBella.
LaBellas are sought after by those who prefer that traditional "old school" bass sound that has regained a bit of popularity lately. I have these flats on my Fender P, and they feel and sound fantastic. The price is a bargain -- Carvin must buy these in bulk from LaBella, because they come from Carvin packaged in clear shrink wrap. My set has been on for over a year, and they're doing fine -- just wipe 'em down when you're done playing.
If you're looking for LaBella flats but don't want to spend full price, this is the way to go.