There is no doubt that blade servers offer tremendous benefits to the data centre; providing high-density computing that in turn allows for a smaller footprint without the resultant power compromise.
However, whilst blade servers take up less space and allow for the deployment of state-of-the-art technologies like VMware they do require some serious facilities planning and architecture development to gain the most from it.
Check out this article talking about blade servers. They remain an effective platform for virtualization projects, but whether they are right for you and your data center is going to depend on a number of factors. As with any new platform, you need to establish how it will work with your existing technology, your existing data centers and best practice.