Interestingly enough, one of the other things that swatches can tell you is if the person who wrote the pattern is capable of writing a pattern that results in the lace pictured in the photograph.
When the work in progress (wip) was not progressing, and I had "used all my lifelines" and it still wasn't coming out right. I gave in and swatched. The swatch didn't balance either. Now I will admit that my first thought was that I was doing something wrong. After all, how much lace have I really knit? Not enough to think myself an expert by any means. So I swatched again. Still wrong.
At this point I began to question both my sanity and the pattern. I googled for the supposedly traditional Shetland lace pattern by the name given on the pattern... yeah, not exactly the same. Having found a sample graph elsewhere (thank you Google!) my swatch from this second source's instructions turned out perfect the first time.
It is also worth noting that among the sample graphs of the new source I found several other patterns which I think I might like even better.