I've been doing all-grain for some time and thought my extract days were behind me. Tonight I have an extract wort boiling away downstairs. I had a hop - Nelson Sauvin - I wanted to test under as controlled conditions as possible. To test, I decided on a simple Blonde Ale and to keep the variability introduced by mashing down, I decided to use the extract from my LHBS. They go through a lot of it so I know it's fresh! It's a small batch so I added some DME to bring the gravity up to where I wanted - a normal 1.056 wort. Since I want to know the character and aroma the hop gives, I bittered with Magnum, about the most neutral bitterness you can get. And since I have 2 2-gallon buckets, I'm splitting the batch to ferment one with WLP060 and one with WLP005 to compare the "maltiness" produced by the different yeasts. This isn't a designed experiment in my professional sense, but a test of a hop and two yeasts. I get to vary only one factor, the yeast, but I still get three pieces of information from the test: Info on the hop and info on the two yeasts. A pretty good outcome! The other factor is time. I don't have to mash, cutting two hours at least off the brew day (or in this case, evening). This lets me run the tests during the week and brew the "big" batches on the weekend. A good outcome! So there we have two good uses for extract for all-grain brewers, tests, due to the consistency of the extract (if that is applicable - check with your LHBS to see how much they use and how fresh it is!) and time, particularly when the ultimate quality of the brew isn't of ultimate importance. And I'll keep you posted as to how the test comes out!