I have to say: I use a DVR in the bedroom, and a PVR (Snapstream Beyond TV, to be specific, and I highly recommend it) in the office. I rarely watch a show live, and I always skip through the commercials, and so I can understand CBS's position on ads and timeshiftng. In fact, this raises an interesting question: are some shows inherently more appealing to people who are more likely to timeshift, and if so, then are those shows necessarily harder to sell to advertisers? I wonder.
The bottom line, though, is that the networks need to develop different ways to monetize their broadcasts.