Text on a path is very cool. It would be nice to be able to drag the starting point of the text along the curve.
No need to drag, you can just push the text forward by pressing space before the first character, or for finer adjustment, kern it horizontally (Alt+arrow keys).
Editing paths becomes very slow, almost to the point of becoming unusable, at high zoom levels, or with modestly complex paths.
I agree that this has become an issue. Can you please create some measurable test case (e.g. a complex path and a time measurement of some action on it) and submit it as a bug so we could track the progress in addressing this.
Text Dialog takes a long time to pop up.
That might depend on the number of fonts installed on your system.
The font used for menus is smaller than that used by other applications.
If it's on Windows then it's no fault of ours. That's what Windows GTK uses I guess.