I had purchased two phones at the end of May and early June that had the notorious intermittent choppy voice quality problem. I called VZW support at least once a month from June through August complaining about the problem and was advised to wait until the Android 2.2 update. When the update did not fix the problem, I called HTC support directly and was given some vague assurances that they know about the problem and that it will be fixed... sometime. HTC also said that they had far fewer reports of problems with more recently manufactured phones.
I then called VZW support, referred them to my previously logged complaints from June through August and asked that they do the right thing and replace the phones with newly manufactured ones. They said that they would only replace them with remanufactured models. Escalating to a supervisor did not help and I agreed to go with the remanufactured units.
I'm happy to report that after about two weeks, neither phone has experienced the choppy call quality problem. The call quality on both of them is the usual, crappy call quality we've all come to expect and tolerate from just about every cell phone on the market.
On an unrelated note, the battery life still leaves a lot to be desired, although I confess to be a rather heavy user of data and other battery draining services.