Apart from the usual Verbatim/MCC and Taiyo Yuden*, Imation-branded MBIPG101 R04 (8X +R) give outstanding results in the 4550. It also does very well with premium CMCMAG E01 (HP-branded for instance).
The 4550 is an outstanding CD burner, great for audio if you burn @8X/12X (very low and constant jitter). It handles extremely well any decent CDR disc, but of course the best results are from TY CDRs.
- I personally don't recommend TY -R for DVD, despite great scans they're IMO very overrated for overall quality. The +R (YUDEN000T02, YUDEN000T03) are much tougher discs. If you like -R, Verbatim is better (still IMO) - MCC03 RG20.