Double 45 degree focus screen

[levihaynes]

I've just bought a double 45 degree focus screen off ebay to try in my canon 50D. Has anyone experienced one of these before and is it better/worse than a single??

I've never used a manual focus screen before so quite excited to see if it makes much of a difference. I've an adaptall 2 adapter, and if I can master manual focus, I will buy some more manual lenses.

Here is an example ebay link