well, as a backup ds for 10-15 bucks, maybe.
but i wouldn't deliberately buy one for much more again.
while the microswitch dpad is wonderful and in retrospect, the start/select buttons were placed very comfortable, the phat had a bunch of problems.
the worst of which is the touchscreen. its so very sensitive, much more so than the lite or 3ds'. even with a protection foil, i ended up scratching the thing eventually. you'll definitely need a solid protection foil.
problem two, the screens themselves. compared to the lite, they're kinda dark and the colors arent very vibrant.
even through an anti-reflection foil (which tend to tone down colors a bit), the ds lite still is worlds brighter than a phat.
its also kinda heavy.
finally, while fingerprints on piano black dslites are a pain, phats don't look that pretty once their colorjob rubs off.
the only thing where the phats seem to excel is their durability, hinges seem to never break (though they get somewhat wobbly eventually) and i'd guess they'd take a fall better than a lite or 3ds
if its a design question... nah.