Very. I have a shared folder with a few classmates for class projects. I have a shared folder for crazy videos/media/Top Gear episodes my friends post from all over (not everybody wants to upload thier vids to youtube for the whole world). I've got a shared folder among friends sharing music (piss off RIAA) Anytime somebody needs a file from me, I give them the DB link. You can run scrips and host websites from DB. I think just the potential to do awesome things, and the simplicity of how it just stays out of your way, means it will hold customers a lot better.
I rely on Dropbox shared folders for exchanging files with some clients. I also use the Dropbox integration of a few essential iOS apps quite regularly. For me, switching would mean having my clients install Skydrive, as well updates to those iOS apps for Skydrive support.
Everyone here is talking as if it's a all/nothing game. I'm using both DropBox (to continue to share with existing people) and SkyDrive for my larger, private stuff. I was able to move several gigs off of DropBox (with no effects with current people I share with) and then downgraded my account. A 2 Gig should be enough for me to share with the people I already share with, and I moved several gigs to MSFT.
Personally, I think DropBox should have had a smaller, paid plan than the $10/50 gigs. I only needed about 5 -7 total.
Problem solved for now, though.
Edit: I should add that my gigs of stuff I uploaded to SkyDrive today took a fraction of the time that my DropBox uploads take (not entirely sure why, but I've always felt DB throttles large files when uploading).
