we bought a new pram before our holidays earlier this year and it came with a wrist tether. It was useful as there were times where we'd be walking on sloping ground etc. It did give me peace of mind however, my added bonus was DH was there to attend to my 3year old. A tether and 3 year old, although well behaved mostly (the child, not the pram, hehehe) isn't always as practical as it sounds. That being said, a tether with one hand on the pram and the 3year olds hand in my other hand......adds a tad more security.

Regardless of brakes and their colour......strangely enough, I trust my hand on the pram and the tether around my wrist more than I trust brakes enough to let go off a pram on any slope! But that's just me and my paranoia