Propranolol is the only drug I have taken for mental illness that I would recommend.
I used it for to prevent or end a panic attack. I am also of the opinion that it only works physically. I noticed my heart rate slowing, breathing becoming easier and muscles relaxing after taking it (but my muscles would still ache afterwards from the spasms - similar to doing a hard gym session!).
It definitely can't cure your anxiety, but as a little crutch for the hard times to pull you out of the hole when you're stuck, it's extremely helpful.
I found it fast-acting but short-lasting. If the anxiety did not subside I would have had to take another dose.
I noticed no side effects although I had to be careful to not become dependant on it and wean myself off while learning to cope with anxiety alone.
I agree that only a GP can give safe advise on any medication.
I also agree that it could have been a placebo effect but it worked so no complaints from me!