As far as keeping stuff hot and being durable, Stanley's are hard to beat. I stopped by Borders book store the other day and in their coffee shop they were selling a really sharp looking red Stanley thermos.

I ordered an Stanley Aladdin Classic l ltr from here here yesterday to replace the Sigg which has been sent back. Arrived this morning!! I can't fault the Thermos except they are slightly heavy (should be tough and robust though). I'm now tempted to get the 1.9litre version for home emergency use and also the 0.47ltr version for outdoor use. The Stanleys appear to be very well made and very thermally efficient. Oh and the 1 ltr version does not leak either. The 0.47 version looks to have the same stopper and cup design as the larger models.

+1 on the Nissan. Made like a tank and lasts forever. I have one that is at least 15 years old.

Thanks all for the suggestions... I was on a site earlier today to pick up some Klean Kanteens for the kids and picked up this guy for myself:
http://www.littleacornstomightyoaks.co.uk/klean-kanteen-wide-insulated.php

going to give it a shot... not expecting too much. But it should be leak proof!

First day with the insulated Klean Kanteen and i'm impressed. Kept my coffee nice and warm for 3 hours. Sides of the unit were cool to the touch (as you would expect) but did notice that the loop cap was warm when I was touching it. Definitly heat loss there but not too much to be a factor for myself.

I will test it out later night and see if I can get liquids to stay hot to the 6 hour mark as mentioned on their site. I can see this being realistic.

On another note, the form factor is awesome for the briefcase and it doens't leak at all (when you use the screw top lid). And it does a quick convert to a travel mug when you get the cafe cap.

Over all, highly recommend it.