My first one took about 4 hours, but 2 hours for the second one. They're not difficult, a little fiddly at times but nothing complicated if you follow the instructions. The plain track is simple as well. I got it down to about 5 minutes to assemble each 0.5m length.
Edit - forgot to add, our club layout is being built with fiNetrax plain track and crossing vees, with handbuilt pointwork. I think there are about 55 points on the scenic section, the majority curved, so using Wayne's bases wasn't an option.