Beagle
NOTE: ASIO4ALL does not use the ASIO drivers of the soundcard with native ASIO drivers. ASIO4ALL is a WDM wrapper. so if you're using ASIO4ALL to run your soundcard which has native ASIO drivers, you're not using that soundcard in ASIO driver mode, you're using it in WDM driver mode but fooling the host into thinking you're using ASIO drivers.
Exactly, so it exposes the WDM driver as an alternative ASIO one which you can then use alongside the interfaces native ASIO driver.
The reason it 'looks' agressive is because Sonar will take that last ASIO driver to be installed (in this case A4ALL) as the new default, hence you'll have to disable all the entries for it in Sonar unless you want them to take precedence.
I know how it works and what it is doing, like I said I use it to aggregate the WDM driver to use alongside the native ASIO one. I don't have any issues with it at all in use ever, but as you say there maybe some system specifics involved with different setups that could cause problems.
If it caused problems I wouldn't be using it.
The thing with ASIO is if you set the output of one application to your ASIO driver when you load Sonar your native driver will be in use and be unavailable. If you set it to ASIO4ALL you can load Sonar and record the output from A4ALL into Sonar without needing Rewire or any other audio bridging solution.
It's very useful particualarly if you use an app such as Reason that doesn't host VST's or if you want to play a synth 'live' into Sonar rather than record the midi.
If you want to mix or arrange on your laptop while you are on the run without having to lug round an interface then it's a must have.