I like it, although I do believe that it depends on the content of your site. If you're a technical person and run a technical site, chances are the ads will be higher paying than a site about video games, music, or other entertainment mediums like that. It may take you 1000s of clicks to make a few bucks with sites like that, where as if you run a hardware forum, you may have fewer clicks but higher bids on those ads, thus making you more money. It all depends.

Thats not entirely true.

Google has 2 different spiders. One is for the Search engines the other is for adsense. The 2 are unrelated. Having adsense ads do not help you get a higher or better position in the serps. The Adsense spider only comes to your site when a new page is called up and an ad has to be determined. All the adsense spider does is check the content of your page for the purpose of matching the ads it will serve on that page with the content of the page.
Regardless what they say, my page has grown in ranks since I added Adsense, so have other sites in which I have adsense on. Adsense bots put the url in their database to be archived, thus they get archived faster.

Ad clickthrough rates on forums arent great compared to websites, so using adsense on even a popular forum doesn't usually bring in impressive results (as i have found out)

I have a about a dozen websites currently active, and the ones that are "retail" it's a nightmare to use Adsense on. My biggest site gets 300,000-600,000 hits a month but when I placed Adsense on it, it showed ads from my competition. You can choose not to display certain website ads, but there's no way to exclude them all. So, I'm reduced to using them on my 'public service' websites. Where I use vbulletin is a site dedicated to a specific tech field & I moved the adsense script to the footer (because of the liquid vs fixed skins issue). It generates enough to pay for maintaining the site and for beer. I like & it works nice in vb 3.0.6.