I have had a LibraryThing account since mid-October 2005. Most of my collection is in there and tagged, and I’ve even started keeping books in my catalog that I no longer own (appropriately tagged, of course), just so I can keep a record of what I have had at some point.
If you look on my blog, you’ll see that I am using the LibraryThing widget to display a random book from my catalog. This changes every time the page loads, and sometimes I am surprised to see what is there. As I’ve noted several times in the past, I have more books in my house that I have not read than those which I have read.
If you’re new to LibraryThing and you have a large collection of books that are new enough to have barcodes printed on them, I recommend you purchase a CueCat scanner. It will speed up the process of getting everything in, and then you can take more time to tag, make notes, or do whatever else you may want to do to tweak your library to suit your needs.
What I have not done yet is to make use of the Recommendations, mostly because of the aforementioned over-abundance of reading material in my possession. Also, I’ve already read many of the books listed or they are already on my wishlists. Eventually, I plan to import my book wishlists into LibraryThing. I am doing that with my music collection on RateYourMusic, and I can see the value of having all that together in one place.