I'm not sure what to think of this. My first reaction is it seems like a solution looking for a problem. My GBA can already run its own cartridges, GB and GBC, and emulate the Game Gear, so that's most of the consoles Analogue lists taken care of. Anything more powerful than the GBA (DS, PSP, phones) can run even more.
Regarding the FPGA and its benefits over emulation, I've never really found that to be an issue with handheld games. I can see how it would be a selling point of Analogue's NES, SNES and Genesis consoles - no lag at 1080p! - but with a handheld? Maybe I'm a little biased, but my favorite games on handheld are puzzles and RPGs where twitch reflexes aren't necessary. And regarding sound, emulators deal with that just fine. You don't need the FPGA to mimic something like the Genesis' FM synth, handheld sound hardware is much simpler.
Similarly I don't see the point of a dock either. This is opinion too, but I don't think handheld games look that good on anything other than a handheld. Like, seriously, who wants to play the Game Gear port of Sonic with its wonky HUD and cramped camera on a big screen? Find a different version that fits better. Even stuff like Mega Man Zero and Metroid Fusion doesn't feel right either. A dock's nice to have, yes, but I don't think it's much of a selling point.
I think the biggest appeal is the second FPGA though, "for developers to develop and port their own cores". If somebody manages to implement the Genesis and SNES on said FPGA, like the Super Nt and Mega Sg, I'd be very interested. A handheld Genesis like AtGames' consoles, except one that actually doesn't suck? I'd buy that. To be honest, I wonder why Analogue hasn't made those themselves, seeing as they've now proven they can fit a powerful FPGA in handheld form... hm.
Not for me, I guess.