Yes, you can switch between tuners, However, you lose the buffer.
The workaround is to set one channel to record and then change the channel to access the other tuner.
I was not thinking about the buffer.
The reason I asked was because last night I was watching a channel when a show came on that was recording that I didn't want to watch live at that time. So, I changed the channel and as you stated it did change to the channel on the other tuner. However, I thought I was recording on both tuners. Big Brother After Dark was supposed to be recording also at that time but for some reason it wasn't so it allowed the channel change. I thought changing the channel had stopped the recording of BBAD.
Now I found out tonight by trying to change the channel when both tuners were recording that it brings up a screen asking if you want to stop one of the recordings and go ahead with your channel change.
Anyway, the reason I asked about switching tuners is because I also have DishNetwork and they have a "swap" button on the 622/722 remote that will switch back and forth between the two tuners whether you're recording or not.
Thanks for the replies.