I've been using flasks for many years, always took one to work and always take one in the tailpack when out on my motorcycle. Often take one when using my bikes as well.
I've used the Stanley flasks in the past and they are good flasks and pretty indestructible, but for that indestructibility they are really heavy, a lot heavier than the usual stainless steel flasks. The other thing i dont like about them, is that they have a really narrow neck, which is better for keeping the temp in, but it makes it hard to clean the inside of the flask.
So i just use the standard steel flasks, either the Thermos Thermocafe ones or the generic similar ones. I also will only use ones with the twist & pour stopper. Many flasks now have the complicated push button stoppers, these are crap, heat will escape through them and because of the design, bacteria will trap in the mechanism.
The Thermos Ultimate are supposed to be really good, but they are quite expensive.