You rarely, if ever, find an album that pleases everybody, and perhaps because of this you may find reviews of this collection elsewhere saying "this is a weak song" "that's not up to standard" and so on. I prefer to take a slightly different view.
What you actually have here, (and I think Ian Anderson said as much in the sleeve notes), a kind of Jethro Tull "try before you buy" sales brochure introducing you to their back catalogue. The CD spans JT's illustrious career, starting with their single "Living in the Past" and progressing in a fairly non-chronological order through some classic Tull and some less obvious choices.
I think this gives Tull newcomers a chance to dip a toe tentatively into this unique band and get a feel for their various musical directions, prior to taking the plunge proper. Once you've found a track that grabs you, all you need do is a little research to find out what album it came from, then go get that album if you want to find out more.
For example, if folk rock is "your thang", you may find "Heavy Horses" or "Songs from the Wood" do it for you, and as luck would have it, these are title tracks from their respective albums. Aqualung, with it's changing time signatures, is more prog rock and the album it's from went in an entirely different musical direction.
That's not to say you may not grow to like either style, but with such a diverse back catalogue to choose from, why waste time trying to get into something that doesn't quite do it for you at first listen? In this respect, it's almost an ideal "first" Tull album.
The other way of viewing this album, is that it's almost like a live Jethro Tull gig in layout. I bought this album after seeing Tull live in 2001, and for me, it's like having a Tull gig in my living room everytime I put it on, with the added benefit I can sit in a comfortable seat and don't have to queue for the bar! I put it on when I'm in the mood for some Tull, but don't necessarily want to hear a whole CD of similar songs - much the same feel as when you go and see a gig.
If you're a long time Tull fan, and have all their previous albums, you might only want this CD if you feel you absolutely have to have everything they ever put out, in chronological order, for the sake of completing you collection. However, you might just want it to put in the car so you can have a bit of Tull without having to carry loads of CD's around with you.