I just thought I'd share with you www.statcounter.com I've been using them for 6 months or so now for website visitor/hits monitoring - and it's great!..

1. It's free.
    
2. It's hidden (you can choose an invisible counter so your visitors are un-aware you are using statcounter)
    
3. It's concise - you can see all you need - unique visitors, page loads, browsers and much, much more.
    
4. It has some great features like the facility to set up a "stats viewer" account which means you can give your clients access to the stats to their website only, while managing all your clints under one admin account.

OK, it's obviously statcounter branded when viewing the stats but for a free, easy to install instant solution to concise website statistics, it's a no brainer!

I believe they make their money from google ads on the stats pages.