DC CRACs, Liquid, Passive?

This entry goes for your comments I always have been an Infrastructure Integrator and designer; so when I meet a DC environment and the customer ask how to solve the hot spots; of course I try to give the "traditional" answer (hot-cold aisles; no open RUs, seal raised floor openings, and so on) after new temperature and flow measures, most of the times it became a better DC environment. However, when you are designing a brand new critical telecom/data space like a DC; you have took all of this "best practice" for the design. Then you realize that there are some other that are "popping up" in the industry or market, like "passive, liquid or just reloaded CRACs type" cooling At this time thinking in cabinets with internal cooling is quite amazing (I know that the "older DC for mainframes where like that) because I have to learn how to design such solution. Other one is to switch cabinets with a chimmeny duct type, it sounds reasonable, however the server deployment from one cabinet to this new one, will be a challenge in most of the actual DC, with no "service downtime windows" available. Hearing Liebert or APC with their proposals is quite interesting, however the server set in the top will continue having a hot spot? Well what do you think on this?
saludos

roberto sanchez,RCDD