There has always been debate on this. My current set-up is a shared and vps hosting for my multiple sites. I read about SEO hosting and was intrigued by the concept. What are your opinions on this sort of hosting? Do you think it really works? I rank pretty well for my keywords but if this makes my rankings boost by a bit. I'll consider buying it.
the general rule i use is separate ip for each niche (or at least not have 2 or more sites in the same niche running off the same ip)
I have a VPS, well a few, but I never pay attention to what sites are on what IPS. I still rank fine. That being said if you are planning on trying to do SEO by linking all your sites together or building some linkfarm thing then I would recommend SEO hosting. I only link a few of my sites together and that is when they are closely related. Of course, if your site gets big enough move it off to its own server anyway and it will automatically have its own IP, but I wouldn't do that until you knew the thing had a good ROI.