I'm excited for this (I got a first round pre-order) - not so much because of the portability, but specifically because of the dock. I have other ways to play all my classic handheld games on the big screen, sure, but I do like the convenience of having one FPGA console to handle the entire catalog of games I have without having to switch devices. The portability is just a bonus. The included music generator is also a nice touch as I have enjoyed the Korg line on the DS over the years and the Pocket Operator handheld music gadgets. Will also be nice to get the PC Engine adaptor when it's released so I can play my PCE library on the go without having to worry with an expensive and finicky Turbo Express.
I haven't liked all the Analogue solutions (I hate the NT Mini - much prefer my AVS), but this one has many features that make it worth it for me personally.