Yep, climbed them all. I think it took about an hour--maybe 1.5 hours because we stopped frequently and looked at the displays and other things on the way up. I felt it was interesting and worth the time. Beware of monkeys! They are a big pain at times but were not a bother as you get toward the top. I also remember that I got a bunch of small Kyat bills (100's I think--but I can't remember the exact amount) and gave one to each of the people who clean the steps--which is a necessary task. I was told by our guide that these people are very poor and this was their sole form of income...so a couple of dollars total from me made these people very appreciative. They are not begging, but rather providing a service. But don't feel any pressure to do this unless you want to.

After we finished and returned down, we drove to a beautiful resort nearby for lunch on a veranda overlooking the mountain.

I agree -- Mt Popa shouldn't take too long to climb or be too strenuous. However, for me, next time I'll opt to spend more time exploring the temples in Bagan -- especially those further out of the way where few tourists go. But you can't go wrong no matter what you choose. Have a great trip!