Different prints are lined with different types of plastic...here's a link to the types:http://www.wrap-n-mat.com/fabrics.php
Unfortunately, the ones that use PEVA (the safest from my research) are MIC. But that's what we use. Reusablebags.com will only sell the PEVA lined, so that's a good place to look if you want to go with PEVA.
Ours have held up really well and we use them all the time and have for over a year. I do have one where the plastic melted a bit but it was my fault for putting something really hot on it. We hand wash our mostly, but I do throw them in the washing machine periodically.
The company stands behind their product and should replace those that have had issues.
Good luck! I hadn't heard about happy sacks. I'll have to check that out!