I'll admit the Clara's backing does seem cheap and plastic-y. I wonder why they didn't use the rubbery backing most e-readers use?
At any rate, an inexpensive sleepcover would solve the problem of it feeling slippery and the sleep/wake power issues. I'm using
this case. It's inexpensive and works fine for me.
The books you are reading, are they ePub or kepub? I only use kepub and haven't noticed any page turning speed issues or unreliable page turns.
I've also not seen issues with slow/laggy UI. Anyone else?