I used to not feel one way or the other about them, and I never used to draw them, but lately I have started a little sketch book to jot ideas down when I think of them (which still isn't often ;). I used to think that I didn't need them and they wouldn't help me so why bother... but when I finally gave them a chance I noticed that they were great for getting the Mojo flowing again when it had been missing, and I also found that when I used sketches I scrapped much faster (which for a slow scrapper like me, can be a huge time saver!).
I still do the majority of my scrapping sketch-free but they now have an honoured place in their own little book among my scrap things.
Here is a LO I did yesterday from a sketch challenge on Concealed Beauty: