I recently had to upload over 10,000 final JPGs to photoshelter and I used the built in upload feature in PM. I had to stop the upload part way through because the cache filled up my startup disk before I could queue all the uploads. Luckily I had an external drive that I was able to use temporarily to hold my PM cache. I changed the cache location and then requeued all my uploads.
I would like an option in the upload dialogue for PM to upload directly from where the file is located, instead of first copying it to cache first. I believe it would help queue multiple uploads faster, as well as not having to worry about running out of cache space.