Generally I feel a little awkward in a new car, but generally by the end of the day I should have the hang of it.
I learned how to drive manual in under a week, and manuals are generally a little more trickier than automatics. Even then, I catch on by the end of the day in a manual as well.
Most of the cars I've owned though have been mid- to compact-sized vehicles. I've owned at least half a dozen and driven at least a dozen different cars regularly.
And FTR, I can parallel park better than anyone in the Midwest.