Google alerts seems to be working too well. I am getting Comments for my blog-posts within 12 hours. I have also been using it for quite some time. Fortunately, they have provided the option for selecting the frequency with which you would like to get updates. When kept at everyday, I had to spend considerable amount of time cleaning up my mails. Their crawl engines are quick in detecting new blog posts. But I still find that they haven't crawled my web-site although I have set all the settings required using their webmaster service. Just hoping they do it sometime soon (although its quite sometime since I set-up the required settings).