Bought his for my HS20exr after much searching and saw that someone on a blog somewhere had been using the YN460II with theirs and it worked fine.
The YN560 also works fine with the HS20exr. It is also awesome. I can't compare it to other, more expensive, speedlights as this is my first one.
The refresh rate is fantastic. I think it claims something like 3 sec but I was getting 1 sec right out of the box and still am with the addition of a battery pack, probably less in fact.
The sound mode only seems to work once the flash is attached to a camera or a receiver so don't be thinking it's not working if you try to play around with that setting without connecting the flash to something. It's not super loud either as I think others have reported - it's just right.
The power/compensation settings are great and easy to use and very versatile with the use of smaller increment adjustments on each setting using the up and down arrows on the d-pad.
Note about the power button. Press and hold it, the lights on the compensation indicator will fill up, there will be a double beep, then you can let go otherwise the flash will just tun off if you let go before the beep. Yes it took me a few goes to figure this out.
The zoom is great. At it's narrowest setting with a shutter speed of 1/4000 and aperture at f11 on iso 200 I have gotten effects comparable to using a speed filter. 1/4000 is my fastest setting on the HS20 so this flash works with all my shutter range with no loss of sync.
The pilot/test button is quite hard to depress but at least it's not going to accidentally get set off. I've used this with a wireless trigger and as an optical slave and all works fine. Comes with a nice thick bag and a stand.
I'm contemplating getting a YN560ex for TTL but I'm almost certainly getting another one or two of these. Love it.