I was initially enthusiastic about the nofollow idea from Google, but I quickly lost that and became extremely skeptical. Now there's a good summary post by IOError on what the outcome of all this has been - and it's not been the problem for spammers that some people initially thought it would be:

As we've seen, rel="nofollow" is Google's way of having bloggers effectively delist themselves from search engines under the guise of protecting them from comment spam. If you want your site to have more Google juice, and who doesn't, people have to link to you without rel="nofollow". It's that simple. Nofollow hurts the entire blogosphere, and if carried to its extreme, will result in most blogs being relegated to obscurity as they drop out of the top 100 search engine results.

Pretty much the size of it. The spammers don't care - so long as there's a link to follow, PagRank is just so much fluff to them. What this has done is de-emphasize blogs in Google's ranking scheme, which is something they've apparently wanted to do. Better yet (from their perspective), most of the bloggers cheerfully followed along.