Naw, speed isn't an issue.... I'm sitting on a rather high-speed line here (OC-3)....
My issue is mostly that :
1) I have to sign up for their regular spam to listen,
2) They cookie the hell out of my browser, (my *nix boxes HATE that)
3) You have to wait often 2 weeks to see a new song that was JUST finished show up, and be 'approved' (We tested the theory that they actually listen and approve each song by posting an mp3 that repeated over and over, 'mp3.com sucks the (edited out due to extreme crudeness)...', they posted it without question, and without any language warning...)
4) Space is limited, and servers get loaded down quite often,
5) The look is SO 90's! The pages are so covered in ads and ugly!
6) They are owned by Universal/Vivendi! Independents supporting the major industry? Ick!
7) You have to p4p for p4p? Huh? And $20 a month? Jeeze, I can get gigs of space with my own domain for that....
Anyways, I won't go on, there's more, lol, but I choose not to associate with them

I'll check out your tunes elsewhere, and if you want another free spot to post your stuff, drop them on the site I run (100% indies, and volunteers running it). You probably already know what it is, and I don't wanna come off like I'm advertising. 'Approval' is instant, who's to say what music should be approved, and what shouldn't... And everything will get more customizable as time goes on. New version due in the next couple weeks (more manageability, etc.)
W.