This is my 3rd goglass bottle and I love them. Sure they're a little higher maintenance than plastic sippy cups, but that's why plastic has taken off in the baby bottle world... I personally prefer to deal with a little more maintenance but have glass bottles.
This bottle will leak if you aren't careful attaching the handles and top. For some reason, glass against plastic is less forgiving when it comes to leaks. Maybe a rubber o ring would help? not sure. But if closed properly it won't leak. Also, yes, it can break if dropped... my daughter has dropped this a few times from high chair height with no breakage. It helps to have the silicone bottom on at all times.
Make sure the little air vent isn't closed or else you'll wonder what your kid is doing as the top gets sucked down into the hole and eventually falls in and then you have to fish it out. But despite any 'issues' this is still the best (and pretty much only) glass sippy cup I could find. I'm glad it's available here on amazon and I'll continue using it until my daughter moves to regular cups/glasses. It also comes in super cute patterns! we have the giraffe, the frog and now this dolphin :)