Okay, a couple other people have said it, but I'll add my two cents anyway.
First, depending on the genre, 30fps isn't the end of the world. It's a big deal for say, shooters, not so much for stuff like JRPG's, since they typically have static camera's during their most taxing moments.
Second, most of these are early beta demos, the developers have roughly five months until their games must be completed, and in all likelihood they'll be in much better condition by then.
Third, the XBone titles, particularly the multi-platform games, were running off PC's, with specs highly in excess of the X1. In reality, most Xbone titles weren't far enough along into development, even to run on Microsofts hardware.
Finally, DF did seem a bit excessively negative in a few areas. For example, they made a fairly big deal about frame rates dropping in Knack, but I only noticed that during a non-playable cinematic scene. Even then, it really wasn't that noticeable. The game could use some extra enemies here and there, but it was hardly a mess.
Basically, you shouldn't look at incomplete E3 demos and expect entirely perfect performance, especially during a launch year. E3 games frequently run less smoothly, even when they're being developed for platforms that developers have spent years with.
All that being said, it's kinda a shame that developers don't give gamers the option to drop the resolution slightly, to get to 60fps. You're always going to have some games that push visuals too hard for 60fps at 1080p. In many cases, you wouldn't even have to go all the way down to 720p to fix that.