I use feedburner to monitor my subscribers. (Or excuse me Feedburner/Google) I am assuming self hosted wordpress? There is stats monitoring of feeds in the free version.
Burn your feed in feed burner and turn on the feed count chicklet. You can also display that on your blog.
Feedburner is the best way to see your feed subscriber, it also provides some other useful info regarding your subscribers
Like everyone here has said: use Feedburner. And install this plugin: http://www.feedburner.com/fb/a/help/wordpress_quickstart
I took that plugin off because it was giving a 307 temp redirect. I wasn't sure if that was a good thing (for seo). I know 301's are ok, 302's aren't, what about 307's?