This was an expected move but it's still a bit weird because there are quite a few features available in Synaptic which are still missing in Ubuntu Software Center, like upgrade/downgrade functionality, lock packages to the current version and so on. But of course, there are 4 months till Ubuntu 11.10 is released so Ubuntu Software Center might get some (or all) of these missing features.A Synaptic - Ubuntu Software Center feature comparison can be found here