I bought a 2000 ES 300 4 years ago from a dealer CPO, and I was glad I had the warranty. I didnt have any major issues, but I feel I did get value from the additional cost of the CPO. I did have to replace the rear suspension which was covered, and everytime I went to the dealer, I was treated better for having a warranty.
In terms of buying a 2000 today, I agree the warranty wont be worth much. I also agree with the other posts. Make sure and verify the service records. After 90K, there is a lot of stuff that could need to be done aside from the timing belt. I just did a major service 90K / timing belt / water pump / cam and crank seals, and now I am having issues with the IACV which seems to be pretty common with these cars. This is a $285 part that hopefully can be cleaned as suggested by the good folks here in the forum. I also have leaking valve cover gaskets which the dealer wants $400 to change.
My point is, you are buying a old machine and buyer beware. No matter how good of shape its in, it will have issues, and unless you are a mechanic, you will have to spend some dough. For around 15-17K, you can buy a brand new scion, which is also a toyota, and will be completed covered under warranty and have piece of mind. Food for thought.