My karma seems to be pretty sturdy, I haven't had any of the issues you see others posting about. But then I don't try to use mine for a hockey puck, either.
I'm quite happy with mine... the only issue I have is the screen issue (it scratches VERY easily). I need to take the time to make myself some screen protectors, though, and since I haven't done that yet I really can't complain too much.
-- Gary F.
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Eeyore, Original Owner -- Mk II 80 Gb, Blue
S/N #090000803
Tigger, 2nd Owner -- Mk IIa, 80 Gb, Blue
S/N #40103789