Ocarina of Time was running at 16fps in PAL and 20fps in NTSC, totally unplayable at least for me so I certainly hope BOTW is more than just a tad better! :/
It felt like 25 fps with fluctuation up and down, possibly some input lag - or maybe resulting in input lag. Baring in mind I only had 10 minutes with it. When I played it in portable mode, it was a tad better I think.
While it looked good (especially in portable mode, but not bad in TV mode either - I was super close to the TV) it was annoying, especially when I attacked.
The grass looks good, seems to fade in well, the enemies were cool and I can tell there was a fair bit going on mechanically...but as someone sensitive to fps and input, it bugged me.
People have replied a few times to say that there are reports of the final version being better than the preview build I played at the event, so there's hope if you're picky about that stuff too.