I never picked it up because of the music replacement issues. If you're buying it blind though, this issue won't mean much.
I saw it in its first run and enjoyed it quite a bit. The chemistry between Katt and Culp is good, and Culp in general is fun to watch. Fun premise too, although when it premiered, I was eagerly anticipating Superman II later that summer as that was the extent of the live action super heroics to be found. With so much of this stuff out there now, and the somewhat dated, but competent, effects work in the tv show, I don't know if new viewers will get as much out of it as we did back in the day. I've caught re runs since then and its...ok. Not terribly compelling, but by no means horrible (at least that applies for the first season...I think the novelty of the show, and Culps character, started to wear thin fairly quickly after that).
I wouldn't buy every season all at once, but the first set isn't that expensive is it?-If it were under $20 that wouldn't be too bad- although I think a rental would probably be the best bet.
I also saw The Greatest American Hero in first run on ABC...but only the first 2 years. When they brought it back after a hiatus period for a short 3rd season (13 episodes), I wasn't even aware it was back on the schedule.
So far I've only purchased the first season used for only $8 (half-price off the $16 used cost) at a Suncoast Video store. The only thing that was out of place was their featuring the 1986 sequel "The Greatest American Heroine", an unsold pilot featuring all of the main original series regulars over 3 years after the Hero series ended. It didn't work that well, but the story was enjoyable. By that time Ralph and Pam were married, and with their new haircuts they looked better....and Bill looked a lot older. More importantly... Ralph had been exposed to the press as having the suit, and being re-visited by the aliens he got it from, he passes it on to a young woman.
I think the Heroine episode should have been held for the third season set instead, so it would have been in order but maybe Steve Cannell wasn't sure the first year would sell as well as it did.