Not actually, raott. I wouldn't say the HR34 has dual live buffers. When I think of dual live buffers, I think of TiVo, where they are active all the time and you seamlessly have a buffer going for your current channel and the last one you were watching, too. The HR34 has the standard DirecTV DVR feature, Double Play, with effectively does the same thing, abet a bit awkwardly. You have to tell it you want to have buffers on two channels going at once.
I did use Double Play last night briefly and it works fine on the HR34. I'm sure I'll use it again in the future. But I'm also positive I'll be more likely to use the multiple tuners in the record mode more. With a 1T drive, I doubt I will be hurting for space any time soon. Who cares if I use up 50 Gigs of space recording four football games for an afternoon? I'll just delete them later and do the same thing the following Sunday.