How can I query the read/write ratio in Sql Server 2005? Are there any caveats I should be aware of?

Perhaps it can be found in a DMV query, a standard report, a custom report (i.e the Performance Dashboard), or examining a Sql Profiler trace. I'm not sure exactly.

Why do I care?

I'm taking time to improve the performance of my web app's data layer. It deals with millions of records and thousands of users.

One of the points I'm examining is database concurrency. Sql Server uses pessimistic concurrency by default--good for a write-heavy app. If my app is read-heavy, I might switch it to optimistic concurrency (isolation level: read uncommitted snapshot) like Jeff Atwood did with StackOverflow.