I got the top tier model at the Apple store (nothing CTO) which is with the 2.8 i5, 8GB of RAM, and 1TB Fusion drive. I've been very pleased with it so far. Granted, it is probably too much for my use (mainly a media server), but it might see use as a main computer in the near future so I decided to get the higher specced model.
The reason I got this model was for the Fusion drive as it has all of the necessary cables/brackets for the PCIe SSD (which appears to be easily removable without taking apart the entire mini) and HDD, 8GB of RAM is more than enough for me, and I wanted the Iris Graphics. It's been working really great, and even is able to do some gaming (newer games with lower specs or older games) without a problem. Yeah, it is overpriced, but that wasn't a concern for me and the overall performance of the machine for me is perfect.
The Fusion drive is really nice and I would recommend this or an SSD. I wanted the Fusion since I will be storing lots of media on it, so the store model made sense to me. Read/Write speeds are super fast on the PCIe SSD, and the machine feels like it is running just with an SSD all the time.
If you get the base model with 8GB and a Fusion drive I think it should move really quickly and likely feel like a base MacBook Air. That was actually my initial plan, but I just decided to go all out. Personally I would just move up to the middle model and add a Fusion drive or an SSD, which is only about US$50 more than a base model with 8GB/Fusion drive.
