Why does there seem to be an interest in the MK1 units?

People like the screen more.

Is there any other reason?

Why is the MK2 better?

I think I remember hearing the MK1 can overclock to a higher speed, but I've only ever owned the MK2, so I don't know the main differences. Let's wait for someone else to reply.

Yes well my MK1 seems to go 300Mhz+ and yet my MK2 only goes at 250Mhz. Bugger!

Is there a good reason to overclock? Won't that damage it?

Is the MK1 worse in any way, and if you had to choose between MK1 and MK2, which would you pick?

Where can I get an MK1 cheap?

People overclock because they want to run demanding software. This generally means emulators for MAME or PSX or Amiga or SNES, etc.
Whilst many emulators will work fine at the standard 200Mhz, some fall under the "the faster the better" adage.
It's common for people to overclock to 240Mhz as most GP2X will do this no problem. Others will find that they can do up to 320Mhz - which is about the highest I've heard of.

Overclocking will not damage your GP2X. It simply will just lock up. Switching it off and on will fix this as it will restart at it's default 200Mhz speed again.

The Mk1 is considered worse because of the joystick, screen and some other reasons. The Mk1 joystick has a diagonal bias - meaning it's often easier to achieve diagonal movement rather than standard up/down, left/right. The Mk1 screen also seems to suffer from interlacing effect on the screen - meaning there seems to be some flicker associated with it.

On the flip side the Mk2 screen is considered to be superior due to better color saturation and contrast although it does have a smaller viewing angle - though application of gamma correction seems to fix this viewing angle problem to a degree.

If you want a GP2X, I'd be waiting for the new Mk3 which has the dpad and touchscreen. Though that means 1-2 months without a GP2X. Considering I use mine almost every day that would be... difficult, at best! So I would understand why you'd want to get one ASAP!

I don't. MK1 screen is a washed out scan-line mess

My MK2 can overclock to 280. Just go for the cheapest thing around. They all have their draw backs and advantages.

MK1 : Not everyone likes the screen, as it looks slightly washed out and has the scanline issue ( I like the scanlines lol ), the joystick is generally considered to be terrible ( not in my case ), and clock rate ( + 300 ) is normally higher than that of the MK2... These units also tend to have badly soldered components.

MK2 : Slightly better screen with slightly worse viewing angle. Much better contrast. joystick is rotated and gives slightly better control. Max clock rates are generally below 285.

I think that this is all , I'm happy with both models

I seem to remember reading that the serial number of the MK1 can be changed with software, but I'll leave it up to a guru to confirm or deny this.

Why would you want to change the serial number?

because it can be done ?

and btw which came first the chicken or the egg ?

Bill Gates probably