Not a lot of folks jumping in with answers to this one... Check the thread here [webmasterworld.com] too.
I'm currently playing with Submission Hawk [submissionhawk.com]. I've owned it since version 2.01 and it was unusable for me at that point. It's up to V3.00B now and it's still crude in the area of adding and deleting URLs to be submitted but offers adequate features in other areas and might be worth considering. I currently use a batch file to dial-up, start SH to submit 5 urls, then hang up and do it again for the next domain... The batch is scheduled to run every 25 hours, it's not elegant but it gets the job done...
NFFC was looking into something he felt was promising early this year, perhaps he has some input.
I ran one of the new submission programs thru it's paces on one domain consisting of 600 pages, 3 url's per day for 45 days.
The aim was to get the pages listed and to try and prompt a crawl. I submitted to AV, Excite, Hotbot & NL. Unfortunately after a week AV implemented the ransom note method, 80% of the pages that were submitted were listed.
Many other domains were promoted at the same time and the vast majority have substantially more pages listed without direct submissions. The only SE that I feel is worth directly submitting to is AV, my auto submitters are in the recycle bin with the exception of DumpTruck for the occasionally blast of other pages that link to my domains.