Alternatively, instead of updating your metafield, add a new one!

Then the problem becomes, which meta has the highest value, and how do I cleanup the other meta fields.

How I Would Do It

Instead of reinventing the wheel, I can see that Google has already done a brilliant job of counting how many people viewed a page. I can also see Google Analyticator even shows me the top 5 and gives me a chart.

So instead, use the Google APIs, or integrate some other existing solution. Even wordpress.com & WP Stats sends the results off to a remote machine rather than hosting the entire stats package and database locally.

Using post meta, or options, or a custom table etc etc is going to slow down your page loads, make your databases size much larger, and introduce many problems, not just locking table rows.

A Final Note On Performance

I would also recognise that there is an inherent trade off here, between speed/scalability, and how fresh your data is. If you have a counter on the frontend that’s 100% accurate all the time, there are computational and logistical costs associated with it.

An approximate value on the other hand doesn’t need to be updated as often and can be cached more easily. Suddenly your program has breathing room and you can adjust the update rate to scale with your site and environment.