Anybody have any experience w/ replacing their Prius hybrid battery?

I have 150K on my 2001 and now need a new hybrid battery as well as the battery that controls the computer. The price is $5000 - $4000 in parts and $1000 in labor.

If I knew I could get another 150K out of the car, it *might* be worth the cost of the repair. But, that's such a hefty price tag I'm wondering if I'm a total idiot for even considering it.

Another option is to replace it with used parts at a cost of about $2000. There is some risk w/ used parts that they won't work. If the parts are warrantied, I can return them to the salvage dealer, but I'll be out the cost of the labor.

Any thoughts on the value of replacing the battery at this point?