My guess is PC for the mouse controls…point and click adventure games don’t feel very comfortable with gamepads…but I haven’t played riven so…
PC.Plus you can get images from the game if ya want 
“Hurry.Don’t listen to my broth…”
That link doesnt work for me but im looking forward to myst 4 anyway, I must admit I never player Exile but I loved Myst and Riven. I also read the book about Aitrus and liked that. Ive also played Uru and although i didnt really like the story of Uru, it looked stunning. I presume that myst 4 will use(or expand on) the Uru engine in which case it should be truly great!
No.Myst IV is not in 3d,it’s basically like Myst II : Exile but with much better garphics and light effects.
members.shaw.ca/baby_y/Myst4Screenies/
OMG!^Those are images from a screensaver which you can grab at gamespot.com
Unfortunatly it’s only for WinXP users 