AC 24-JAN 20:03 is correct
I've worked for IBM and Dell and have hands-on experience of HP, IBM, Dell and several other X86 vendor products, having consulted in this space over the last few years.
IBM's custom chipset in the 4+ slot machines although interesting when it was first released is inferior to that now provided by Intel with their latest chipsets. I think that IBM didn't feel the need to keep up, or couldn't justify the R&D.
AC has a point on systems management - Dell's Open Manage has come a long way on their regular servers and anyone in the X86 space who hasn't taken a look at their new blade product will be pleasantly surprised - Mac/IP assignment to slot Flex IO and 17th blade for management. You can get more from IBM but you have to pay for it via Tivoli. Director is free and it's got most if not all as Dell's free stuff, but it's not as simple to use for installation and maintenance in my opinion.
AC is correct regarding price point - IBM is unable to compete in this space with Dell. It's the same as the PC business - they got out of consumer because they were unable to compete. They got out of the business PC business because they were unable to compete. IBM is making money (very good money!) globally on services, mainframe, software etc but not in the X86 server space. Why else would they turn this over to Lenovo?
I have a concern about the future - is Lenovo buying existing design IP? Rumour had it that OBM laid off most of the blade design team and has moved to an ODM process versus an OEM model. Will Lenovo just do to the same SE Asian design houses and cut out the middle man?
Street price right now favours Dell over IBM. As a consultant, I constantly advise IBM customers to get a quote from Dell - and to let their IBM reseller know that they are doing that. Even if they are not serious about switching, the Dell price will be an eye opener and the IBM price will go down significantly.
Regarding the comment about PSU's, Dell has had best price-performance for quite a while - they also have an Energy Smart range of servers with high efficiency power supplies and other components (HP and IBM do not).