If you want to mill the occasional smallish log then I would say a chainsaw mill would do a good job. If however you want to mill large logs on a regular basis I think you would soon get frustrated by the speed of cutting. When I used to use mine we milled alot of large oak up to 36in diam, it did the job but I was young in those days. You need the most powerful chainsaw you can get.
I think I have posted this link before.
http://picasaweb.google.com/lh/photo/_tYU5OGVqdwURJeYI46zNw?feat=directlink
Best to get me in with my new toy
http://www.youtube.com/watch?v=B4pvQKR8tmQ