I ended up getting the 2.7GHz i5, 8GB ram, and the Fusion Drive.
So far I have been very pleased with the performance of the machine.
There is a very noticable difference with the Fusion drive vs. a standard HD, but once the Fusion drive is full and things start rolling over to the standard drive, things will slow down some with large files, but I still think it is a good upgrade if you don't want to put the money into going with just a SSD.
I use both FCP X and Motion 5 and have had no issues with either one.
However, there are a couple of caveats here:
I also use external USB 3 hard drives which helps vs. just doing everything off the Fusion drive.
Almost all of what I do is limited in length. Motion projects seldom exceed 30-60 seconds in length and FCPX projects normally run no more than 10-12 minutes (church announcements etc.).
If you are going to be working on larger projects you might want to beef your specs up a bit as David suggested.