Firstly - look at the cost, yes fairly expensive but they really do a great job. Im not just saying that, it took me some convincing by reading other reviews and visiting the site FAQs before buying these and parting with 45.00 from amazon.
They fit really good and the online size guide is spot on. Im normally a 34 waist and it suggested a medium based on my height/weight, which fits really well.
I have used them for the gym and for a 15 mile walk yesterday. Everytime they have stayed put and dont ever fold over or slip upwards like other shorts may do.
To be honest you hardly notice them when being worn and they do look really good, plenty of people take time to have a look as you go by.
Sweat management is very good as is cooling - so you are never wet or cold.
You can wear these with or without underwear, on their own or with a pair of shorts over the top.
All in all an excellent product and would recommend to anyone.
Just make sure you wash them on delicate / cold with no softeners as I do with all my sports gear.