Having worked on a couple of e39's now, they are well built cars, and designed to be worked on after the production line, something completely lost on the French.
However they do have similar issues to omegas. Bushes and suspension issues are magnified 20 fold as there's considerably more components involved to go wrong.
Leaking cam covers on the petrols causing misfires.
Diesels have the calamitous swirl flap issue (which the omega doesn't) and the fuel system runs at massive pressure meaning filters galore to change in awkward places after each stage. Injectors are enormous and expensive to re-con. However the weasels don't sound like weasels at all. Quiet, refined, with a nice turbo whistle as it spins up. Sounds like a proper machine rather than something off a farm.
Hedgehogs fail and door membranes leak. Display panels pixels fail. It's more car, arguably, but it's more to fix and a bigger bill.
They'll do similar miles to omega. But the running costs are considerably higher.
.... what turns the drivers into arrogant arses I'm not quite sure. Just watch one come on from a slip road. Oh BMW IN COMING, PREPAR TO BRAKE!

.