Nissin Di466 flash any good

Yes I've used one for years now. It's fine for me, though keep in mind it's the only flash I'ved owned. TTL works fine, and any Olympus or Canon compatible flash cable gives you TTL while off camera, should you want it.

The downside is that it doesn't swivel. Pricier flashes do. So if you wanted it to keep the flash attached to the camera's hotshoe and bounce flash off ceilings and take photos in a portrait orientation, all at the same time, you can't with this one.

 

I have one, seems to have plenty of power, but being used to Nikon and Fuji flash metering and ambient balancing, I'm left a bit disappointed when its only my Oly bodies. Not sure if that situation would improve with an Olympus branded flash, I suspect it wouldn't.