I take this thing everywhere with me because it actually fits in my cup holder! I use mine all the time for cold drinks and i got my dad got one for hot drinks; we are both really happy with the cups! I use the straw lid and it seems leak-resistant (I can take the straw out, put my finger over the hole, and shake it and nothing comes out) and he uses the other lid, and it seems to be leak proof! the lid is pretty thick, I think to insulate better, and if you've filled the cup too full, when you put the lid on, your drink will ooze out.
Rating: [5 of 5 Stars!]