I've been playing it in normal mode. That was pretty awesome, especially the last room with the borg queen. I do love the fact that it requires creative thinking. The Borg really adapt!
The first room's difficulty should match the other stfs one, and is a good tutorial.
The second one with the virus is maybe too easy, the borg special attack in the circle could use more damage in this one, and the spawns are lame. This part could use a buff.
Something making the last part unplayable in some undetermined circumstances: 80% of the room and the whole central part of the platform was a forbidden zone (the green one on ground killing you instantly), and I couldn't escape my part of that grid in tme. You should tweak the pattern of that attack so that we can always escape in time to reach a safe area. Otherwise this last room is well balanced and a little challenge for experienced players with a new way to play the game.
One negative thought: the STF is rather short. One or two waves could be added in the last part. That's a quick run but very enjoyable.
Haven't played it yet, but my main problem with Ground STFs is that they're too long. If this one's "too short", I think I might be happy with that. Too long = much more margin for error, esp. with a pub team. Further, too long = much, much longer when a newbie messes up - which will happen, they're new.
I can't wait to try this out (tribble's not working for me) though!