I use gandi and am quite happy with their UI. BUT don't, DONT open 2 domain zone in 2 tabs to edit them. Gandi don't support that : you will end up making modifications for domain 1 while thinking you are modifying domain 2 !!
+1 on Gandi. A very nice UI, and I like having my registrar outside the US. As a DNS host, it's robust enough, but they don't provide SPF records (~ 6 months since I've looked.)
SPF records are just TXT records, which they do support?
I understand theres an actual "SPF" record type also but last I checked its not very widely adopted and the TXT version is exactly the same anyhow.
I bought a domain from gandi.net recently and was very impressed with its ease of use and the speed that changes occurred. All I wanted to do was point the domain at a linode instance and everything was live within minutes. Very fast propagation. Early days, but impressed so far.
(I wish they offered .com.au though)