FWIW - as best as we have seen the Astra S and Astra are pretty much the same device just tuned to different focal lengths - ASTRA S is focused on the 0.4m to 2.0m range while the ASTRA is 0.6m to 8.0m
If 1.8m is your sweet spot then you would maybe be better off looking at the ASTRA - it works very well at the 1.5m-2.0m - the ASTRA S would maybe be getting near the edge of its focal range.
BUT - having said all this - currently orbbec themselves have only limited support for GESTURE tracking - they do have a deal in place with Gestoos for access to their gesture system - but the licence seems and little odd and requires re-registration every couple of months - and gestoos seem more interested in pushing people towards their retail point of sales HTML5 based system than their c++ version which has not been updated in forever.
ALSO it only supports visual studio 2013 AND to be honest from all our testing its pretty unreliable and crashed a lot - it seem runs quite slowly and is limited to 320x240 resolution.
Having said this - once you get it setup - if you dont mind that it seems to take forever to start up - and can live with low resolution - it is reasonably effective at tracking - but again its gesture recognition can be somewhat hit and miss - L and Point are ok - but open and close / grab detection seemed very hit and miss.
The body tracking system that orbbec has released themselves has I would suggest more long term potential - but right now it only tracks joints - so Head-Shoulder-Elbow-Hand - it cant track fingers and right now doesnt have any gesture tracking capabilities.
However, we have just finished a working pointer GUI for one of our game engine implementations which works quite well once you get it tuned and have some filtering on the motion data - and can track both left and right hands at the same time - of up to 3 people - based on the body tracking sdk.
In terms of tracking - the performance of the body tracking sdk on a astra is very fast - with quite low latency (25-30FPS) - BUT - in our testing the ACCURACY of the tracking is more of an issue - this means - that even when holding your BODY or HAND perfectly still - the tracking point jumps around quite a bit - - adding a filtering algorithm or a moving average window algorithm can help this considerably - BUT you then start to increase the latency - by the length of the window.
AND well finally - right now its ONLY c++ - we have looked at couple of options around this - either a wrapper or a virtual joystick implementation which might suit your needs.
Happy to have a chat offline if you like.
Westa