These are my first Gore-Tex Boots and after a few hundred miles of riding in the Humid TN summer...I'm not sure I buy the hype. When I wear these boots my feet do sweat some but not excessively. I do not feel any temp difference when riding through cool spots which I thought I might given the extensive venting to the liner.
Sizing, these fit true to the size chart for me and matched my other boots size.
The toe cover TPU was very stiff against the shifter at first; but seems to be loosening up.
I tried the TCX air tech Evo Gore-tex boots at the same time and Picked the Sidi's. First the TCX seemed over 1 size too small despite having followed their size chart. Also the TCX has a HUGE velcro inner flap that was uncomfortable and awkward. Finally the Sidi just looks clean and attractive while the TCX looks like a bunch of random panels stitched together in the vague look of a boot.
Verdict: I wanted a good three season street boot that didn't turn my socks into a sponge if I come across a rain storm. The Aria I think fills this bill well. You do pay a price in heat vs a nice vented boot so if you only ride when it's hot and dry save some coin and go with a vented version.