Glenn Alsup over at the Viewmark Blog has a great post on how it's next to impossible to properly satisfy all user needs with a single analytics tool/data warehouse. I've blogged on this theme before, but it's worth hammering home time and again, since it's diametrically opposed to what the vendors want you to think. The problem with BI is knowing the information requirements prior to users using the system. Given the role of BI is to support decision making, people don't know what they need until they start to work through the issues - the very thing the BI system is supposed to support. No data warehouse design, however big, is ever going to be able to anticipate the specific information requirements needed by a decision-maker, especially if the decision is a strategic one (the real sweet-spot for BI).
My personal view is that it's better to spend money on a team with some great analytical skills than a software solution that ends up as a glorified enterprise reporting tool. In many decision situations, small-scale, non-permanent 'ephemeral' systems (so-called 'personal DSS') thrown together to answer specific questions are more useful than multi-million dollar BI systems. But then that doesn't sell software licenses, consulting or support contracts.