I've uploaded about half of my photos from our trip to France to Flickr. The thing that's holding me up from finishing is the only application I use on a regular basis that isn't yet universal—Keyword Assistant. And it's not even an application, it's a simple iPhoto plugin that makes adding keywords to photos quick and painless, and then FlickrExport converts the keywords to tags when I export to Flickr.
It's killing me not to have Keyword Assistant. I've sent Ken an email or two inquiring about release timeframes, et cetera, but I haven't heard back. This functionality is very important to me, and I'm willing to pay for it.
If someone wants to create a similar plugin for iPhoto, you've got one licensed user waiting in line. And Ken, if you release a new version, I'll gladly send you some money!