How good is the original 5D Mark I compared to the 2013 Canon's?

It's a lot better than pretty decent, especially for £300.

I've being using mine since 2005 and whilst on occasion I've had thoughts of upgrading it, it's not been because of image quality. I could have done so recently, but choose to upgrade my 70-200f4 instead.

The big prints I've made from it still look fantastic to me and I've no need to print bigger.  I'm talking 33x22" on paper and 48x36" on canvas.

I would like a higher-res LCD, but for me that's not enough reason to upgrade.

I've read a lot of comments on here about dust, but I've never found that to be too big an issue myself, especially since I got an arctic butterfly brush,  My D70 and S2 were far worse.

The AF also comes in for a lot of stick, but is fine for me, I use the centre point and one shot most of the time though.

I'm not saying it's as good as a Mk3 or D800, but for me it's still good enough. I don't need 36MP nor do I need to shoot at fast shutter speeds in dim light without flash!