can you have a decent trip to kyoto in one day from tokyo? we were thinking of taking the bullet train down and back. or should we do a 1 night stayover?

I'd say at least 1 day stopover. It depends on what you wanna see, obviously Kyoto is crammed with temples and shrines etc etc, so if you wanna see a lot of them then have at least one night stopover

It is possible to do Kyoto in one day out of Tokyo, but it will be tight. If you catch the first Shinkansen Southbound out of Tokyo (06:36, assuming you are using a JR Rail pass), you'll get into Kyoto around 09:21 and have enough time for an attraction or two before lunch and maybe another 3-4 before the daylight fades. A lot of the "must-see" spots are spread out at opposite corners of the city, so you'll need to allow for the subway/bus/walk times to get there.

If you stay overnight, you can go at a more leisurely pace and do some walking - it's a really nice place to explore on foot. When I visited Kyoto, I was staying at a relative's place about 30-minutes away by train, and one day was not enough.