Yep, used the ST-E2 for the last two years and found it good indoors and fairly short range. It's an optical system so needs line of sight to work so you need to make sure the receivers on the flashed have that line of sight which can mean a little bit of rotation on a stand to keep it. That's where the flash head swivelling comes in handy!
Outdoors that can be a little hit and miss in bright conditions and the further away from the flash the flakier it gets. That's when I use PW's and go manual.
The ETTL functionality is good and the ratio feature is excellent.
There are better systems out there though and radio plus ETTL is pretty much the holy grail of flash funtionality.
Hope that helps.