We have some problems with Proximity:
The detection of the beacons is very slow although the beacons where set to 100ms advertising interval and full signal strength.
There is a delay of up to two seconds. Can the detection rate be increased in the App? I didn’t found anything about that in the tutorials?
Is 2-second enter delay not good enough? 
We’re doing a good deal of signal processing in Proximity SDK for better reliability, this might be introducing a little bit of lag. You could reduce that if you roll your own Bluetooth detection code without any signal processing.
Some lag comes from the Bluetooth hardware and system drivers/APIs themselves, and that’s something neither our nor your code could change/deal with.
How do you plan to use the beacon signals?
No, because users are… users 
If I use Estimote (and I like the hard- and software very much) that I don’t want to write any Bluetooth related code, if not absolutely necessary.
We have an app and the beacon signal is activating some functionality that can’t only be used in a green zone (as defined by beacons) so detecting the zone activates the functionality. Then we tried to define a exit zone, where the functionality must be deactived. And there the two second delay is not good enough because if the user is going a little bit faster the exit zone is never triggered…