well this is my assesment of the 3vo vs the evo. i think the build quality of the 3vo is top notch. the only complaint i have is the charging port location being on the side of the phone. but other then that i really like how the 3vo feels in my hand.
the screen is an odd shape. it should have stayed the same dimensions as the og evo. it makes typing a little harder as the keyboard has to be squished due to the size of the screen. the screen to me seems a little bit more on the yellowish side compare to the evo's screen (i guess that will depend on what screen you had on the evo as some of them have a different type of screen). it is still very bright.
now as far as speed and performance goes, this phone just plain out flies. it is very smooth, no lag. and that is just stock! gonna be flashing some custom kernels soon to see how much i can overclock it.
call quality is no different that i have noticed.
as for the 3d thing.....well it is 3d and it is pretty neat. it was not my main reason to get the phone.
well for battery life, i can't say as i rooted my phone within the first hour of getting it home. but there is not many custom kernels yet anways so...right now i can get maybe 12-14hrs off charge. and that is with playing with it a lot, since i just bought it recently. so not too bad, i guess.
i mainly got this phone because my port on my evo is getting very loose and it was only a matter of time before it crapped out on me and also because i knew i could root my phone. i was hoping for the devs to support the device for the rooted community. there are not that many roms out, but more and more devs are coming around. i'm excited to learn that the cyanogen mod team is working on a cm7 rom. i just hope that some day mik will come around to supporting the 3vo.
so overall the 3vo is an amazing phone. i think that stock wise it is better then the og evo. but if you have a rooted evo then i think that you would have the advantage right now over the 3vo.
i hope this helps anyone thinking about using your upgrade to get a 3vo.