I released a document so you guys could knit a swatch for the Birthday pi, even though I don't believe in gauge when it comes to lace. Why did I do it, you ask? Well, since you guys will be blindly following me, I thought it would be a good idea for you to try your hand at it. Doing a swatch also helps you decide if the yarn/needle combo works for you.
Don't get me wrong, swatches are important - for a number of reasons, not only gauge. When it comes to lace, gauge might not be so important, but a swatch is still recommended, as by knitting one you can figure out if you like the fabric you're getting.
For most people, when we talk swatch and gauge what comes to mind is counting how many stitches/rows we have in a predetermined measurement - like this: