I did try out a number of SP104 and SP105 T-mobile (German Telecom) firmwares and found that they are really poor. 3 Italy was a pretty poor firmware, as I had problems logging in!
Polkomtel's SP103 was a solid performer, but after a round trip, I went
back to Telia's SP102.
Please drop me a comment if something is wrong or new columns should be added, or if I'm missing a firmware in the list. My idea is to try to keep this up to date with firmware information and I will appreciate any help from you.