I am not a huge fan of using plastic, even BPA free plastic so these dishes with the glass lids are great for me. I love that you can bake a lasagne or something that needs to be covered for part of the baking and then uncovered for the last few minutes, it saves you messing around with aluminium foil.
The only glass bakeware I have found that also have a set of glass covers. Really durable, easy to clean, have the 2 year warranty but its unlikely you'd ever need it.
Nothing, except that I wish these were available at more shops (I got mine online).