I have memory stick and can answer a few of your questions, memory stick
pro operates at a lower temp and possibly higher ambiant temp, something
like 32f vs -15f, the pro is possibly faster. Now the Duo mess is just
that. Many new sonys use Duo, my memory sticks wont fit a Duo slot but
Duo fits memory stick. So if I buy a new sony my cards are worthless.
The regular memory stick is old, forget it, Memory stick pro wont work
on older sony computers that read memory stik. If I had known this I
would have gone SD, SD is universal. But of course sony has to be
different, like BetaMax and the new HD DVD wars. Now I see sony
computers offer SD slots, so are they going to dump stick eventualy?

Answers inline:

Memory Stick, in general, is a flash memory card developed by Sony and
SanDisk.  Its like an SD card but in a different shape.  Mostly used in Sony
cameras, PDAs, Play Stations (?) and digital Walkmans.

Memory Stick PRO is a faster version of Memory Stick.  Older devices might
not accept MS Pro.  My 2001/2002 VAIO laptop wouldn't, and I had to do an
annoying firmware update.  Now it will accept MS PRO cards, but, it doesn't
read them any faster.  Quite slow in fact.  A newer device designed to work
with Pro cards will be pretty quick however.

MS Duo cards are about half the length.  This is probably an attempt to be
more competitive with the smaller SD cards that are so popular.  Sony makes
an adapter that allows Duo cards to be used in devices designed for the
longer MS cards

Many MS cards say "Magic Gate."  This means they are capable of DRM (digital
rights management), which mostly has to do with storing legally downloaded
copyrighted material, like songs.  I don't think it affects performance, but
I think most MS cards sold today have the designation.

It appears Sony is making more newer devices to work with the smaller DUO
cards.

Pro is faster than non-Pro, and there are compatibility differences between
the two.  A Pro device will accept the slower regular cards.  A non-Pro
device won't accept a Pro card, and if you're able to do a firmware update
the Pro card gets read very slowly.

Duo cards fit into regular MS slots with an adapter.  Regular MS cards won't
fit into a device that takes Duo cards.

Magic Stick doesn't apply to digicams.

Nope, see above.

Welcome,

SteveO, a former Sony digicam owner who sold his camera after getting fed up
with all this MS stuff.

I don't know.

There is.
No.

Some but not all.