I like shopping Joann's for trinkets/tools as well as for certain notions, plus their rolls of cotton batting with a 50% off coupon is cheaper than any of my LQS's by far!
Rulers, bias tape makers, marking pens, pins, etc are all cheaper at Joann's as long as they're marked 40-50% off. If I need to get notions like ribbons, rick-rack or buttons, I buy those at Joann. I do a lot of applique work, so I buy my Wonder-Under there -- LQS doesn't even sell that. And, of course, their Warm & Natural batting.
The only things I really try to steer clear of are their fabric & threads. I used to shop exclusively at Joann (fabric is much better quality than Hobby Lobby) until I brought home fabric from LQS for the first time. I was hooked! Too many of the warmer colors of Joann fabric are so thin you can't use them for applique because you see the underneath fabric right through the applique so I used to have to layer or fuse with muslin to make them work.