It would be a lot better if avast improves the ability ot detect more spyware like NOD32 does.
My personal view is that Avast should do what it does best, protect against viruses. In this instance I'd much prefer a master tradesman, rather than a bloated, jack of all trades, master of none.
There are certain things that nod32 does better, but I don't think it has the level of overall protection, email, outlook, p2p and IM, nod32 doesn't do all that (as far as I am aware). Otherwise why would you be using/trying avast instead of nod32 (cost perhaps)?
Adaware and Spybot S&D are great, provided you keep them up to date.
But one of the best froms of protection on the net is common sense 1st, avast 2nd and a good firewall 3rd. For most cases spyware is a hassle but much less important in the scale of harm it can do.