There's also the possibility that custom apps will crash a generic hardware configuration. What kind of support can I get from IBM if I'm on a shared virtual server? Probably not much, because there's not much it can do without putting other customers' apps at risk. This is the trade-off of sharing computing resources.
If you think your organization would benefit from IBM's services, find out a whole lot more before you tell your CIO that you can save the 30 percent IBM is claiming. Or you might just discover the answers the hard way.