We have/had strakes on our UH-1H. The report from the Aircraft Research and Developement Unit (ARDU), aussie equivelent to Pax river, is not as positive as the comments above. It provided no tangible power improvement. It provided better pedal authority in some wind azimuths at HAUW. I don't believe the stability issues were that different. This is all from memory after attending briefs, reading the report (about 4-5 years ago) and ofcourse flying the aircraft.
On the other hand NASA and the Kiwis were very positive about the benifits. It just wasn't reflected in our testing. My own experience operating High and heavy on operations is that it makes ****** all difference.