After updating one of my WP sites to 3.3 I've had endless frustration with the media uploader. It only seems to work with very small images ( >200k is safe) and you have to upload only one or two at a time. As a photographer I'm used to uploading several hundred megabytes of images at a time. This is one of the ways I use WordPress.
So I was glad to see that there was a media upload-related bug in the trac ("Multi-site Upload Limit Stuck at 50MB"), and as soon as I saw 3.3.1 is out, I updated to that and tried out the new media uploader. I dragged 4 2.5 mg jpeg files onto the uploader. The first file uploaded just fine, and then the second one stalled out at 10%. This is the same behavior I've had since I went to 3.3.
This is a huge hassle for me, and I won't update WP any of my other sites until this is fixed. BTW, I do not have any of my sites configured as multi-site.