They are far too 'clunky' as an entity - they have all of the component parts to make great products, however none of these parts talk to each other properly, so when there is a product that tries to bring several of the different brands together it invariably ends up shite.
Take a look at the Xperia Play as the latest example - it was supposed to be the playstation phone, however due to what appear to be internal squabbles the playstation brand never even made it onto the phone in any meaningful way. Perhaps this is justified given that the phone appeared to be crap, but I can't shake the feeling that if Apple were making the phone, the two departments would have worked together until they got at least the full suite of psp games working on it. But it just wasn't in the interest of the playstation guys to help out, since it had the potential to cannibalize psp sales.
Maybe this will get better now that SE will be 100% Sony, however taking into account that SE was the only Sony company to ever release any meaningful cross-branded products I'm not so sure that there will be any improvement.
But I would love to be proved wrong - always had a soft spot for SE. I think before they try and work on the cross-branding Sony need to get something other than a mid-range phone out of the door - I'm not sure why but each new SE flagship is always about a year too late specs wise.
Edit: Just realised I am completely off topic - oops!