fusion drive question for new mac

If you have the funds ($3K), this is a good set up.

The fusion drive will speed up things; my MacBook Air runs off its 256 GB SSD, and the speed versus my more powerful MacBook Pro is very noticeable.

My only query would be the 3TB fusion. I'd go for the 1TB fusion, and then use the savings for external hard drives to serve as additional and backup storage. You'd get the same speed advantage (the SSD part is the same, I believe) but I'd be concerned about how much you'd lose with a drive failure. While drives are reliable, an internal 3 TB goes over my comfort level of potential for disaster vs. convenience. Also, according to the fine print Boot Camp does not work on the 3TB fusion drive (don't know if that's a factor for you).