Personally, I had to remove and replace the batter several times before it finally powered on and I could back up all my files.
Plus, if you call HTC and file a ticket, they will replace your power button for free, even if it isn't under warranty, as long as you haven't rooted your phone. The only drawback is that you'll be without your phone for ~10 days. At least that's what happened for me in the US.
Once I got my phone back, I installed lock widget so that I can lock my phone using the widget rather than the power button. Hopefully it will make my power button last longer this time around.
I haven't tried any of the other apps such as the ones that turn your volume or trackball into power-on to wake up your phone. I'm a bit nervous about if that wouldn't wear out those buttons too. At least HTC admits theres a problem with the actual power button and will fix it. Don't know if they'd do the same for the other buttons.