I bang this drum frequently, but let me bang it one more time: you should be A/B testing.
37 signals should be A/B testing, because they have the volume to do it.
Many of us don't, or aren't sure. Anyone want to comment on what sort of numbers you should be looking at, roughly, in order to get statistically significant results?
A conversion must also be a real sale, by that, I mean people make the mistake of using visits or free signups, and the landing page is optimized for clicks and free accounts not revenue. A perfect example of a failure here is Adwords.com. The Adwords landing page is designed to get people to signup for an account, rather than to generate revenue. 99% of adwords signups lead to dead accounts, because google does a bad job of setting customer expectations on the marketing site.
People like easy answers, though, so my easy answer is "A/B testing is worthwhile if you have 100 visitors a day. Otherwise, spend the bulk of your time finding 100 visitors a day first."
This is a very important point. We've found you have to go with your gut until a point.
We've just started doing lots of A/B testing for Buffer (http://bufferapp.com). We are now getting 300-500 signups per day, and we currently have around a 10% conversion so you can work out how much traffic that is. We've tried A/B testing in the past without success, and I think now is the right time for us with the right volume for A/B testing to have a significant impact.
One important thing: we've started A/B testing aggressively (a new test almost daily, now onto our 4th test. We've tested 3 different variations and had no significant results. I expect this to take a long time, and posts like this make it seem easy to get significant changes in conversion. A/B testing is hard.