WAIT!  DirecTV will be announcing their new, ALL HD system soon.  The sats are up and have taken over the *standard* programming (i.e., the old [20+ year old] sats have been replaced), and the new system is supposed to be available in the spring.  It will use different fequencies, and the standard-def programming will still be available for at least several years.

Anyway, going HD today would mean getting set up for the old system, with only 20 HD channels and MPEG2 compression.  Given that the new system is so near release, it isn't worth it unless you MUST have HD now, or unless you don't think you'll be able to (or want to) afford the new system.  Expect it to be someone expensive, with a likely installation charge and somewhat pricey equipment, since it will be all-new and "premium".  But no one else is going to be able to touch it, as it will have hundreds of digital HD channels.

-Troy
SBCA & WildBlue Certified installer