Would anyone be willing to share their experiences with building kits
from these companies? Any comments on flight characteristics of these
planes? Reliability? Any information to share? Reputation? Etc?

My dad and I built an RV-6 (slowbuild kit) in 5 1/2 years, finishing in
Nov. 2002. Construction can be a bit of a pain, especially if you have
never worked with metal and/or don't have the right tools. It's not
really hard, just tedious and time-consuming. Also, earlier generations
of plans were sometimes hard to read, but with the newer kits
(RV-7/8/10) they've improved significantly. Support (both from the
community and from Van's) is excellent; 4000 kits means they've probably
seen almost everything by now.

Reliability is mainly determined by the systems you put in. Case in
point: other than tracing a couple minor leaks, misfitting panels, or
balky MP gauges (all after dis/re-assembly for painting), we've never
really had problems. Another guy put in glass panels (front and back)
in his -8, a FADEC, butt-warmers, etc. I don't think he has 100 hours
on it yet, and it's been flying for almost two years now. He spends the
time he could be flying fiddling with the avionics package and shipping
his engine off for troubleshooting.

Flying one is an absolute blast. Fast, maneuverable, and (for a
taildragger) fairly docile when landing. Very tempting to live out your
fighter pilot fantasies...