it is. that's exaclty the reason why the initiator of this wants it to move to kernel space.
he has actually running an own kernel version running in the automotive industry exactly because of this. dbus as daemon might not be too slow for desktop systems but it is when it comes to embeded or low power devices.
and it might also affect scientific calculations in some special cases.
p.s. would helpo a lot if people would read more than the headline. a slightly deeper look at the background could answer a lot of questions and solve a lot of misassumptions.
If I remember correctly, D-Bus was (still is?) about 17 times *slower* than ORBit (CORBA), so it needs all the help it can get...