I have 95% of my domains registered there. Overall, I think they do a pretty good job. I have had a few minor problems in the past. I'm sure I would have minor problems anywhere you register names.
I used to have names there when I first started out, had some issues and tried to get help many times via Live Support, I dont know if it was just me but I felt like their Support staff didnt know anything about Domains or the Company they worked for, never could get a straight answer from them.
I no longer have names with them nor plan to any time soon.
Excellent, I have used godaddy,namecheap,domainsite,ev1,enom to name a few and prefer them the most. The 24 7 phone support is very cool and the cheap transfers I like
I've used RegisterFly for some time now, I haven't had any problems with them really except once when I was unable to register a .ca domain extension and asked for a refund which took them forever.