It is helpful. I use it on my google blog. Nice stats and reports for a free tool to use with a free blog.
Register and link your site in...you'll either love it or hate it, but the data it gives is very extensive, it's just a question of if you find it useful and like the presentation.
Its good but i'd prefer it be in real time and that it had a better referral tracking section i also wish i was able to view a particular visitor's pages visited in order etc so i can analyze but i guess i have my logs for that.
I give it a big thumbs up. For a free tool, well you are providing Google your site's traffic stats, you can't beat it. I prefer Omniture's capabilities but there's no comparison when Omniture is ridiculously priced and Google Analytics is monetarily free.