No probs Sharon - I've used miles of the stuff for EPP and the quilt (my daughter's!) is still in one piece after umpteen washes! I also use it to machine piece and as a bobbin thread when quilting. :D
Re poly/cotton, I think this is really down to personal preference. I know a lot of quilters love to use some of the speciality threads which are poly. Personally, if I'm using cotton fabric (and I nearly always do!) I prefer to use cotton thread. I believe there will be a 'tension' between the different materials otherwise and the stitching may develop stress points. Plus, I just 'like' working with natural materials wherever possible, although I occasionally use poly wadding for wall hangings, I only use cotton for quilts. JMHO! :D