If you Google for "mp3 ripping service", there are Google ads for several other firms that offer similar services:

Rip Digital - about $1/CD, but they put a "unique identifying mark" on each track that "does not degrade the sound quality of your music". Uh huh.

MusicRip - also about $1/CD. Nothing about watermarking, one way or the other, but generally less information on the web site.

Moondog Digital - about $0.80/CD, but has an explicit disclaimer that they're not responsible for the quality of the ID3 tags. Weak.

Get Digital - prices range from $2/CD down to $1/CD in bulk, but they have extensive verbiage about the quality of their ID3 tagging, including CD cover art. A nice description from a customer here.