I just upgraded to replicant 4.0 a few minutes ago. I've been running
replicant 2.3 on my Nexus S for about six months or better. I was having
issues with it freezing and rebooting and found it quite irritating. I've
recently realized that those symptoms are common to android in general and
not just replicant.
It is kind of annoying that wifi, gps and bluetooth don't work. On the other
hand though I'd rather have those not work and have more freedom than have it
the other way around.
Overall though things work quite well and it is the most freedom-friendly
solution out there right now.