reprint - 5:14 pm on Jan 8, 2009 (gmt 0)
They are semi in synch. WP MU lags behind WP because Donnacha gets lumped with most of the work whereas for WP the workload is spread out more.
It fulfills a need for me for relatively small sites that are related to each other. I keep them logically organized because if and when it comes time to sell, it is easier to sell the package as opposed to picking individual unrelated domains out of MU and dumping them into WP for purposes of sale.
I heard of the other solution, ergophobe but never gave it a go.
See what you think of MU now. I would be interested to hear your opinion.