Yeah, it's a shame to lose The Documentary Channel. Although, I was annoyed when they started showing infomercials for 8+ hours/day. I liked them better when they were non-commercial, they had a lot of interesting Canadian documentaries I hadn't seen before. The closest thing anymore is possibly KCETLink TV (national feed), or maybe WorldChannel.org. Free Speech TV & MHz WorldView have filled their schedule with news / information series and cut back on the documentaries these days.
I wonder now with KCET behind it if Link TV will be able to pick up any digital sub channel affiliations with PBS stations. It would be a nice addition to the Dish/Direct carriage.