The problem with such services is the actual inclusion rate and the spam you receive afterwards as most directories use a common email prefix like webmaster / sales @domain.com when a site is submitted to confirm the submission. It's worse with search engines as they just add you to their list using a prefix email too - just that they are more aggressive.

Personally I think it's enough to be listed in DMOZ and the top search engines like Google / MSN / Yahoo and maybe a few local ones because that's where the traffic will come from.

It's great if you offer such a submission service, but in the end the only valuable item in your offer is backlinks from a few directories not using nofollow tags.