I have a Premiere project composed almost entirely of After Effects imports. When I export however, even if the effects are just color correction or curves, it takes more than two hours when it takes only 20 min. in After Effects (drag the project into AE).
The CPU usage in AE is 100% but only about 30% in Media Encoder for Premiere (it shows 4 After Effects processes with only 1 being used).
I'm exporting and editing in MPEG2 in both cases, upper-field interlaced.
I once heard that Deinterlacing in Premiere CS3 forces the rendering to singlethread (and unchecking it did push CPU usage back to 100%). There is no checkbox in Premiere CS4 - is it possible this is always on now?