I think the simple issue with the laptop or anything else you're afraid to check is to NEVER put it in a bag that you can't fit under your seat.
As someone else has mentioned, it's not the monetary value of the laptop at issue but the data on it. And yes, my laptop is encrypted, backed up, etc but If I lose it, my company is still in for a world of hurt.
You just never know what's going to happen and I for one always like to have my laptop, wallet, etc close at hand.
I've had this happen on a CRJ before. A woman came on with a HUGE bag and the flight attendant told her it would have to be gate checked. Well the lady freaked out and insisted that it couldn't go below because her laptop was in it.
She also refused to take her laptop out which resulted in a comical standoff. Eventually she just gate checked the bag, laptop and all, cursing the flight attendant the whole time.
Anyway, sorry for the rambling post. Slow day today.