I've never noticed that it's slow - although I tend to resize everything to 1200x800 before uploading.
I'd imagine that most upload constraints are caused by the upload capacity of the user's internet connection, particularly if it's a big file?
I've got one set of pics to upload when I've fettled them and I'll report back with some upload speeds.
EDIT: cancel that thought, it looks like I've accidentally deleted the whole lot 😞
Hello again darkness, my old friend...