The other reviews here may scare you off, because yes, these glass mugs *are* on the fragile side. Only a month or two after buying a two-mug set in a brick-and-mortar store, one of the mugs cracked, and it wasn't because of my usual fumble-fingered handling. That is, I didn't drop it or do anything naughty. The mug just cracked and had to be dumped.
But we liked the mugs so much -- and fought over the remaining one -- that I had to order an additional set.
First, they really do keep your coffee warm for longer than the standard coffee mug. And they're pretty, in a functional sort of way, with a comfortable-to-the-hand heft. They hold a non-wimpy amount of liquid, so you can pour yourself a big mug full of liquid-of-choice without needing to get up for a refill. Yet even with boiling hot coffee in the mug, you can hold the mug in your hand comfortably. Plus (and I confess this was a selling point for us) they're short and squat so they fit under the spigot for our espresso/coffee maker.
None of these are earth-shattering features. But I liked the mugs despite their fragility, and you might feel the same way. I'll just be especially careful with them.