I've never had a problem upgrading before my "scheduled" upgrade was up with Verizon, but count me as one of those that is completely content with the TBolt for now.
I'm very interested to see some of the new ICS models this spring, and we'll see if any can tempt me.
Right now, I figure I have a great phone that runs fast (at least for what I do), has a huge development community that has put out some great ROMs and kernels to really get the most out of it, and I'm still not sure that there are any other devices on Verizon that can do simultaneous voice and data.