Well, this is a bit of a tricky question. It is clearly not them at their best (live wise), but as a hardcore Zeppelin fan, it was an essential purchase for me.
Don't get me wrong I do like it, but there is just so much better out there on bootleg. As mentioned HTWWW is from a similar time period (72 as apose to 73) and I think is a far better concert performance by the band.
Saying that I'd take the 1st disc of BBC Sessions over them all, I love early raw Zeppelin sound, if you can get it, a great concert is the full Playhouse Theatre Concert (I taped it off UK BBC Radio years ago) from 27th June 1969 and it even has a nice little interview with Jimmy and Robert half way through the gig, while on stage.
I'd actually say if you were thinking of buying the TSRTS, go for the DVD, it is far more fun seeing them play the stuff live, inter cut with their rather silly little fantasies!