Hot really, as its much easier to do development with the handy emulator.
The flashcart starts getting useful if you do things the emulator cannot do correctly.
Like testing sound, graphix/contrast, comlynx and the 1% hardware features which are not implemented correctly in the emulation. Firing up th emulation is much faster than flashing, as you always have to switch off and on the lynx, plug unplug cable, etc.
For 95% of the game development phase I use the emulations, only the finetuning i do with the flashcards and/or BLL comlynx interface.
Dont get me wrong, it is really avery nice thing of hardware and i like it! But from the "it will attract more developers" point of view, I (sadly) do not share your opinion... at least it will not "break borders" which developer might have prevented in doing somethig for the lynx!
apart from that ... well ...
Its always nice to see it on the real machine anyway. in that sence it is really nice to have a flashcard where you can show things around. and it does much more fun to testplay on the real hardware that in the emulation.
So, from the fun point of view its a big improvement! And in that sence it could attrackt more ppl!