I have had one for the past few months and find it very useful for commuting. I can wear a suit (jacket in top box) under the coveralls to work on the bike and stay dry, warm and protected. It's also useful to move between locations during the day. I haven't fitted a back protector but the knee, hip and elbow protection are fine. The main zip has a solid fitting at the bottom and if you don't get the suit just right, the bottom of the zip can press into your thigh when walking.
I've ridden in -2 degrees Celcius on a couple of mornings with only the addition of a polar fleece jacket under the suit. I've also ridden a few times in heavy rain and there's been no leakage.
I've a size XL which is just a bit long in the leg for me but on the bike the knee armour is in the right spot.
The other good thing about the one piece suit is there no gap for cold wind to blow up under the edge of a jacket.
I was not convinced of the value when I have good quality tailor made Gortex jacket and trousers (check out the element range at www.tigerangel.com.au)
. A $300 off special deal (normally over $1,000 Australian) at the local BMW dealership made me change my mind.
The one piece would be a pain to wear when touring while it is ideal for commuting. The pockets are not patch type pockets on the outside of the suit so it's like squeezing all the normal touring bits such as spare glasses, spare ear plugs, camera, phone etc into the pockets of a pair of jeans. It's also doesn't offer the flexibility of a jacket that you can easily take off at a fuel/coffee stop.
I've yet to wear it in summer.