When I recently wrote How to get your old fast Gmail back I had assumed that using the old UI would correct the slowness that I was seeing. And it did - to a limited extent, but it wasn't as fast as it used to be, and often crashed Firefox if left open too long.
After investigating, I found that disabling my very own GTalk Emoticons extension resolved the issue. It must be that even though Google preserved the original UI, it is incompatible in some way with my extension.
So my standing advice is to DISABLE OR REMOVE GTALK EMOTICONS if you are experiencing a slowdown in Gmail with it installed - I know I did.
I have no immediate plans to create an updated version of the extension - however, if there is enough public outcry, I just might.
Sorry for the inconvenience. :(
Got something to say?
or, read what others have said...