It has worked horribly for me ... Dr seems to think I have a sensitivity to beta blockers and now put me on a calcium channel blocker (Verapamil) ... which does not control my heart rate while standing, but if I lay down it goes to 40BPM! ... So I'm not taking it anymore and waiting on a call back from the electrophysiologist to see what he thinks about my next medication. So far Florinef, Atenolol, and Verapamil have all failed. The only thing that has been working (after 3 dose changes) is Midodrine, which I don't even thinks helps that much, but I guess a little is better then nothing!
I took Atenolol several years ago for POTS. It worked well for controlling my tachycardia but I had to take small doses. Then after awhile it didn't work for me and the Dr. had to change it.