I'm afraid I'm going to have to disagree with you here Fridge (didn't see that coming, did you?

)
First of all I will say that I admire Hemispheres tremendously. I will agree that it is a very good album and worthy of a place of honour in anyone's collection.
However, to call it their best work I think is a trifle escessive (that honour can only be given to Moving Pictures in my opinion.)
What is wrong with Hemispheres?
Difficult to say. Once again, I think the production lets them down a little. Without being a poor job, it seems a little flat to my ears and doesn't posess the crispness of their best works. I think the problems they had getting the sound together shows and an easier mixing for the album would have lifted it higher.
Like many conceptual pieces, I find it slips a little too far on the side of pomposity. While, in moderation, this isn't necessarily a bad thing, I think Hemispheres goes a little too far.
However, my main criticism is a purely subjective one. I can't say why exactly, but the album doesn't seem to flow in the way that MP or 2112 does. For all that the tracks lead directly into each other, the joins are not seamless and do seem a trifle forced - almost as if they were trying too hard. A number of my friends, also Rush fans, have commented similarly in the past.
That said, side two is a work of genius. Both Circumstances and The Trees are excellent rock songs and La Villa Strangiato is pure virtuosity.
All in all, great stuff but could have been better.
'Do not despise the snake for having no horns, for who is to say it will not become a dragon?'