I have owned a Tablo 2 channel device for over 4 years. Initially, I had problems with reception and buffering that were resolved by careful attention to the antenna and direct wiring the Ethernet connection to the devices.
In the meantime, the Tablo team has been steadily upgrading the software and firmware. Not weekly, but often enough to let you know that they are there and still upgrading the original boxes. The latest upgrade, which allows you to quick view other channels and then switch without dropping back to the main menu is a highly desirable feature that seems to be working well.
The purpose of this post is not to dismiss the concerns or issues of other users, but to reinforce that the Tablo team is continuing to upgrade and support the devices and software, and has done a great job to date.