When the Gretsches first came out, there was lots of buzz about them in the forums, and they seem to like em over at Hawaii Music Supply. Past that, I haven't played one myself. But if we can be real for a sec and share real world opinions about what we really think about a brand... whether well-founded or not....
I've never had a Kala that was too great. All but one of them came from a good shop that does setups, and you could see a setup had happened, but still didn't sound great. The biggest heartbreaker was the jazz tenor. It feels sooooo nice to play, and you'd think that being one of the pricier Kalas, and the fact that it HAS to be plugged in to be heard as it should, that it'd have good electronics. Nope. That and the bridge cracked and lifted. The most open natural sounding one was the Mighty Uke Movie limited model, and that one isn't for sale anymore.
There was a time that for the price, that was the best you could expect, but now there's so many more options, like that Gretsch you mentioned, or a Mainland, or Ohana. I've had great awesome spectacular luck with Mainland and Ohana.
Now someone will no doubt chime in and tell you how what I said is a load of huey, and that Kalas are awesome. Maybe their Kalas are awesome, and you should take that into consideration absolutely. But that doesn't mean I'm wrong about the ones I've had. (4 - never again)