Hey CGartist!
I use DeepMeta (
http://www.deepmeta.com/) for my vector uploads on iStockPhoto.

It's not perfect, but it makes things a lot easier as I'm able to copy descriptions and keywords, save work-in-progress stuff and much more.
It's not very well optimized for vector uploads though. (in fact, you'll notice that it says that it does NOT support vector uploads) As such, I have to upload everything via the usual route first, and then edit their information via DeepMeta. I then complete the submission via the iStock website, and then re-update the keywords/descriptions. It's a little cumbersome, but it's better than nothing... especially when you're uploading 20-30 vectors at one shot -- every little bit of help counts!
Hope this helps!