My dear missus just bought me the RCA box set for my birthday, and what an absolute joy it is. Beautifully put together and designed, with a whole host of brilliant bonus tracks (including some great live appearances on BBC radio). And the remastering really makes a difference - everything feels crystal clear and fresh. If you can afford it (and for what you get, it's not a bad price), I'd highly recommend forking out.
I picked up the box set. I'm not "overly rich" but I treated myself because, hey, it's Nilsson. Set is great and quite a bargain, considering you get 17 discs. I don't know what retail price is but I got it for under $100 USD. The cases are actually mini replicas of the LP jackets, so they are very cool. Sounds great as well.