Hi Neil,
In my opinion, absolutely (not necessarily a reducer, but definitely a field flattener). The two flatteners that I have had relative success so far with is
i. Hotech SCA Flattener (no reducing factor)
http://www.iceinspace.com.au/forum/s...ad.php?t=80765
ii. William Optics III 0.8x Flattener/Reducer
http://www.iceinspace.com.au/forum/s...ad.php?t=86746
I have used both the above with my ED120 and ED80 and both are keepers!! I did have a play around with the William Optics P-Flat IV, however, I could not get any decent results with the ED120.
The other option, of which I have heard favourable results, is the Skywatcher/Orion 0.85x reducer. These work quite well, however they thread directly on to the draw tube and require a M48 ring to attach the camera to.
http://www.skywatcher.com/swtinc/pro...1=5&class2=512
Hope this helps,
Cheers,
Daniel