I would use them with a HDTV. I always want better sound on all my TVs and sometimes it just isn't plausible. Using monitors would eliminate the need for a separate amp hidden somewhere.
I'd also love to see some powered wall mountable stereo monitors geared more towards HDTVs. Something like the Def tech mythos series, but powered. Most of these HDTV speakers are all single speakers that mount under the TV, not a stereo pair that can give better separation.