Well thought and written.
I'm exactly in one of the situations you're describing: I don't have that much free time (school), I have almost totally lost motivation (I have pending updates that have been waiting for months that I make them, which is only a matter of hours... and I was planning to port an old game I like, but I won't, at least on TI-68k calculators), and my areas of interest are drifting.
As David pointed out, TI-68k platforms are great for learning low-level or mid-level (true event-driven cooperative multitasking - not event hooks) programming on embedded platforms. Indeed, one has to take everything (speed, space, screen size, UI, etc.) in account to try and use the full power of the platform.
But as a CS student, I know that I have to learn things on my own, mostly on other platforms, because what I'm taught at school is not always quite enough to find a job (nothing on Perl, Python, Ruby, etc. in my courses - but we've studied Prolog, for example).

On a side note, see how great the GP2X is for games - and it's an open platform running the Linux kernel, unlike that PSP crap which Sony keeps proprietary, closed - and costly.