I have one, too, and love it! I've noticed the bobbin is touchy, but I haven't purchased any particular kind -- I have noticed I have less problems with my old metal bobbins from my last machine than I do with the lighter plastic ones, if that helps anyone!
I have yet to try it on heavy fabric, and I'm happy to hear that people find it works OK. I've been wanting to work on Amy Butler's Weekender Bag, but I know in some places you've got to sew through 6 layers!
So happy to hear of everyone's love for this little machine. I got mine (the blue one) at Sears, too, for a total steal!