Yeti,
I did level 1 CSS early this year, Lily and TP-996 were there also, and TP has gone onto level 2. I didn't know what to expect to be honest, but by the end of the day I'd learnt so much, I would recommend it to anyone.
Why did I choose CSS over ESS? no idea, I guess the main one could be the ESS doesn't do much up North, whereas CSS seem to do most of their days at Rocky or SS
I'll be back for level 2 and possible 3, 4 next year depending on finances etc