Ask HN: time spent testing web site visuals - how big is the problem?

We, at http://42coffeecups.com drafted a little internal tool to help us spot visual changes (especially unwanted ;) as we push new version of web product to server.

I wonder how big this problem is for others. Is it worth enough to create a service around this?

Please, leave your email at http://signup.eyevalid.com/?lrRef=vzb7O if you want to discuss it further.