I was under the impression that both the 550 and 530 have the semi-matte/semi glass (your choice in wording (Is the glass half full/half empty type of thing, lol)).
I can't comment on the stand not being a swivel, and I know the 530 does not have the "WiseLink" feature.
Also, the 530 DOES have side mounted speakers (so Ideally better sound).
Aside from that, I think these TV's are identical.
There is a separate owners thread for the 530 with some comments on PQ and such (They all seem to be positive so far )