Thank you all for the additional feedback.
I have some spare batteries for my 10.1, although I had already switched from one battery to another during the technological issues. Will try again, however (or maybe the batteries just need to be replaced?). I will note that it's been harder to get the batteries in and out of the battery area (needs some jiggling and shaking to get the battery moving out).
To clarify, the 4-year warranty was on the 10.4. That is still available at Best Buy on clearance for $560 (plus $110 for the warranty).
I ordered the 5.3 from Glazer's and it shipped today, so it will hopefully be in my hands soon. (I clicked on a link from an interview DPReview had with it earlier this year...perhaps the forum will get a bonus of some sort?) There's a 90-day warranty (MPB offers a 180-day one), so I don't think it's going to be a dud, but there was no long-term warranty I could purchase for additional peace of mind. But the camera was such a good deal that I'm willing to take a gamble on not having an extra warranty.
Of course, my spouse thinks I should have gotten the OM-5. "Why did you get a used camera?" Of course, I'm the more frugal one in the family.

It's just a hard mental leap to pay about 2.5x more than my previously most expensive camera, when the 5.3 is less than 20% more.
I'll report back once I've had a chance to try the 5.3. I imagine it'll be such a big leap from the 10.1 that I'll be super happy with it...and if not, I can always do a return and get the OM-5 at that point.