You shouldn't worry, at all! Glass bottles are simply better for both baby and the environment. They are way easier to clean and keep clean. And, they don't absorb odors (soap and/or milk).
DD was fed with Evenflo glass bottles for about 2 years and we never broke one. We dropped them onto a variety of surfaces, too. These surfaces included tile, hard wood and concrete (someone bumped into DH while we were shopping in Whole Foods

). I should add that we never let DD hold her bottle (she was always held and fed).
And, if you are really concerned, you can slip on a silicone sleeve. Here are some examples. But, make sure to shop around for the best deal...

. These all seem to be available in a variety of sizes (standard and wide neck/ small and large sizes).
Silikids:
http://www.silikids.com/indexSiliskin.html
Born Free:
http://www.newbornfree.com/ProductInfo.aspx?id=5144033
Evenflo:
http://www.diapers.com/Product/Produ...roductId=17394
P.S. I think the above example of the LO dropping the bottle, it shattering, the crib side falling off, and the LO tumbling onto the shards of glass is more of an example of a freak accident rather than a reason to not use glass bottles.