The editor isn't all that great and the toolset hasn't been updated since it was added. However they've been doing a ton of work on it for Neverwinter and claim to be bringing it over into STO this June/July so we'll see. After all the broken promises I'll believe it when I see it though.
I do hang out with a bunch of authors though, and here's a nice list of some good foundry missions
anything by the following authors:
Havraha ("Rema Donna" is a sequel to the Cryptic mission "That Which Divides", and the Helna missions are funny, she will show up in some other foundry missions as well so I recommend learning about the character here first)
XR-377 (A Will and a Barclay is hilarious and feels very TNG though the big joke is that Barclay's daughter is responsible for the fact that we went through 8 months of having duplicates of our Bridge Officers running around our bridges until Cryptic finally got around to fixing it)
I also liked the following two series. I don't remember the authors name for the second one though.
The Dissent series by Drogyn1701
Resting Raptors, Caged Raptors, Raptors Ascenthttp://starbaseugc.com
is pretty much the best Foundry resource out there.