Yes, I am currently using some items I acquired from them, for my 11 year old (6th grade equivalent)...we use their reading list for high school and get the literature books on half.com or amazon.com since they often cost less there. If I can't find them at those places or used bookstore...then I see if it's not a 'keeper' if I can get it at the library. Most books I consider keepers becuase I will homeschool #2 and don't know if we'll be near a library or reliable postal service at that point...some years down the road. Maybe on a boat? Aside from literature, I have Draw Today program, Rosetta Stone, Singapore Math, Winston Basic Grammar, italic cursive program, analogies...
as for Preschool!
Because I've been satisfied so far, I do plan to purchase the preschool curriculum lock stock and barrel from them come spring when my little one will be close to 2. There are so many books! I think it's a real bargain, that is, if you have the $ to spend towards books in the first place (if not, library and second hand remains best choice of course, using their catalog as a guide). I will supplement with math manipulatives material (fun stuff), puzzles (I like the old SIFO puzzles, find them on eBay), and arts stuff like playdough, construction paper, etc. I think there are some items in the Sonlight catalog for preschool arts and music. We go to music school for my oldest so probably will do something with the little one too. Either piano or violin, whichever he seems most attracted to...if not then dishpan percussion will rule.
I don't think you can go wrong with Sonlight. Except if you have extreme aversion to Christianity, then I think you would do better by picking and choosing from their items offered than buying the whole curriculum flat out, since you'd discard a great deal, or be burdened by reselling it. Sometimes you can get a good deal on the whole curriculum on eBay, but you need to check the contents against the catalog and make sure you're getting everying.
You can probably use the basic preschool curriculum for a few years...ages 2, 3, most of 4 I would gather too...just adding on more math, music, arts and crafts as you go. If you don't plan on having another preschooler, if you take good care of the books, they resell very well. I will keep because we plan to become foster parents when kids are grown, and also to have for grandchildren and little visitors : ) (Big age gap between kids here.)
Hope this helps! Maybe more info than you wanted? I think I like Sonlight because it assume the kids are intelligent and the materials don't waste their time, cater to their natural curious instincts, and leave plenty of time to be kids... they don't treat the kids like little academics, yet they don't talk down to them either. It seems to be a very cooperative and respectful curriculum all around. The offer different choices for different learning styles as well. ie not just one math program.