Since managing to recover the botched 2.23 upgrade, my MiFis behavior seems a bit better. Specifically, I've not yet seen the device just hang completely as it did before.
What I'm seeing now, however, is the device getting stuck in the dormant state. That's happened twice now. The first time it took a soft reset (restart in diagnostic menu) to get it back. In the second, a forced disconnect/connect was sufficient.
Searching the forum here I see some evidence that this is not completely unknown behavior. is anyone else seeing it *after* upgrading to 2.23?
The other thing I saw last night was that Verizon's DNS servers were not responding. I was still able to get to the Internet and the workaround was to configure the Google public resolvers at 126.96.36.199 and 188.8.131.52 on my computer, but a couple hours later it seemed better.
I see it occasionally .... and rebooting the device has usually solved it. It seemed more like a Verizon netowrk problem than a device problem. With this hardware and the ongoing firmware issues, it's difficult to tell for sure.