When working on files that resides on slow file systems (such as remote network drivers) sublime behaves very poorly and sluggishly. I guess some file access is done on the main thread that causes unresponsiveness if file access is slow.

Anyone else experiencing this?

In general, no blocking IO is done on the main thread except for file saving. You may have a plugin installed that is doing blocking IO.

One exception to this, if you’re on OS X, is Cocoa itself doing blocking IO to look up the file icon. This only occurs when switching files, however.