I've had my Eris since March and have been very satisfied with it. As a pda, it does everything I ask it to and more, its only when you start using it as a phone that you bump into issues. The dialer is very laggy and I think the "silent call" issue is as much related to those problems as the 2.1 update.
Personally, I think a number of Eris users, me included, installed leaked versions of the 2.1 update prior to the official OTA. The leaks updated HBOOT on the phone to a version that wasn't rootable under any known exploits. However, a phone updated to 2.1 by the OTA stayed at HBOOT 1.47 and was still rootable. People seeking root were claiming they were suffering from the "silent call" bug to get a 1.6 device that they could then root and update via OTA. Leakers regret.