OK, so I finally got my DevLicense, and the first thing I did was to slap the test engine onto my iPod Touch.
If you've tried that, you'll probably found exactly the same thing that I did.
...that, rather than going "Weeee!" it went "... plod... plod..." at about 2 frames a second.
This is not a good thing.

Today I've been experimenting with all kinds of things.

I've figured out how to draw images to a "buffer", and then have that buffer be one of our UIImageView things, so that it can be drawn over and over again.
I've also found that having 50*full-screen UIImages runs at about the same speed as 50*32x32 pixel images.
Seems that the bottleneck isn't the size of our images, it's the system trying to deal with all the "physical" objects.

Maybe I can fix that later, but right now it's not an issue..

Essentially if you put those two pieces together, you can make yourself a lovely scrolling background image (drawn onto a big buffer), have a lovely scrolling foreground image (drawn onto another big buffer), a few more parallax layers on even more buffers, and then slap them all together with about 40-odd sprites sprawling around the screen.

That's probably not an EPIC amount, and if you wanted a Bullet-Hell type game, it's nowhere near good enough... but for simple scrolling tilemap, with half-a-dozen bad guys, a bunch of pickups, and you...
Well, yeah.. that's plenty for now.
We're still learning!!

I'll post a bit of info on how this all works, at a later point in time.
Gotta neaten it up, first! It's a MESS!!!