Using FPS as a measure of your UI's performance is equally problematic. FPS is a great measurement for for games since performance dips usually occur over a span of many frames, but for UIs a lot of work tends to get concentrated into a single frame. A single frame that takes 110ms (or, heaven forbid, 500ms) to render won't move the needle on your FPS meter, but it will be instantly recognizable by the user.

I've complained about this before; use maximum frame delay [0] instead of FPS when measuring UI responsiveness.

[0] The maximum time elapsed between any two sequential frames during your test.