Hi Harry,
There are a few complaints of collapsed cones on the Gretsche resonators, IMHO so buy it from a dealer with a return policy, if that's what you want. You'll have to either get a luthier or parts if you want to adjust the action or if there are cone issues, but if you take a look the Gretsche it has screws on the handle of the coverplate so you may not have to take the cover off. The fellow playing his has taken the handle off but I believe you have to know what you're doing to do that to avoid damaging the biscuit-cone and there's no way of telling what else, if anything, he's done with it in terms of adjustment to accomodate his nimble playing style.
But if you look at the tailpiece, they are understrung - the string goes under the tailpiece, not over -so another issue I've heard on other forums is string buzzing with the Gretche.
If you are in the market for a woodbody, biscuit cone you might want to consider in the UK's Michael Messer Blues 28, which are properly constructed along the lines of a National and I believe he sets up through Dave King and checks each one and offers support for issues directly and through his forum.
Hope this info is useful and either way, hope it works out for you and if it's the Gretche that there are no issues.
Harriet
