One thing we found around here is that though the Goldberg stuff does fly great and are, for the most part, classics, make sure you re-enforce the fuse behind the wing. That seems to be a weak point (on grass fields anyway) in the design. We've seen various models break in exactly that area on a less than smooth landing. Simple quarter stock and some light ply make a world of difference.
I finishing up a Sukhoi kit, been at it a long time. I found the plans didn't match the dimensions of the kit but customer service advised me that the paper was thermal so would change shape. Problem was the wood was too short for the plans. Other than that I didn't have too many issues, other than a few already mentioned. I wanted to build it the "old fashioned" way and used carpenter's glue. Now I know why people like CA
Still glad to have done it that way though; something different.
I do have to mirror the other folks on the SIG kits. Quality product and solid customer support but don't give up on the Goldberg kits just yet; things can and do change.
Best of luck.
Bob