Downloaded, installed, works nicely....
Well installed here (remarkably quickly) with no issues.
For a detailed analysis of the update, the marvellous anandtech does the business:
Interestingly they point out how the iPhone 4 works well with much lower signal strengths. So maybe the corollary of having an antenna that can suffer from attenuation is that it can work better at lower strengths.
By putting the antenna on the outside, there is the possibility of working with worse signals. However, you can also get your "bags of salty water" a lot closer to the antenna, so the attenuation is more.
Speaking as someone who lives in areas of dodgy signal, I am happy that there is a way I can hold the phone for maximum signal strength. Saves standing on the toilet seat hanging out the window to get that text to go....
Of course, now that I have a SureSignal, the problem has gone away anyway.... ;-)