Tail Bloater,
I may be biased, but there are really no disadvantages to flying Notar. There are quite a few Notars in the UK and I am sure those familiar with them that post here will agree.
The azimuths you mention are called "critical azimuths" for crosswind operations,and vary for the different aircraft depending on the controlability demonstrated at certification. If I remember correctly, the 520N does not have a critical azimuth. Restrictions for the 600N and 900/902 are based on gross weight, density altitude and wind speed and direction. The controllability issue is running out of pedal travel. Although I have not experienced it I am told that the slight loss of antitorque effectiveness is only felt untill the aircraft weathervanes.
The 900/902 critical azimuth restirction does not begin untill 5000ft DA at gross weight.
To me the safety of the Notar system greatly offsets this issue, but I would be very interested to hear other comments.