I just updated a large EE 2.5.2 install to Assets 2.0 and updated indexes. Everything went smoothly, and I've noticed a strange new behavior: thumbnail generation (any size) in the admin panel will temporarily block the website from loading Assets images.
Choose a large (100+ item) Assets folder to browse in the admin panel. Any view/thumbnail size will have the same effect.
While the thumbnails are loading, navigate to a page on the public website that uses Assets tags in its template.
The result: the page in #2 will stall until all thumbnails in #1 have finished loading. Immediately after finishing, the public page will load.
This is on a MediaTemple DV4 server with 2048MB RAM and plenty of resources, and several httpd instances. Could the mysql process be the bottleneck? What else might cause this to happen?
Edit: This appears to be limited to the same session. I originally tried this with Chrome 24 (Mac), running both #1 and #2 in different tabs. When I instead tried #2 in Firefox, there was no blocking and everything loaded as expected. Now I'm not sure if I've got a problem worth solving or a minor annoyance to live with.