I believe the Focus ATX "learns" it's shifting over time, but in 500 miles that should be way over and done with (assuming the new fluid perhaps has a different "slipperyness" than the old.)
Ford Sez: "This vehicle is equipped with an adaptive Transmission Shift Strategy. Adaptive Shift Strategy offers the optimal transmission operation and shift quality. When the vehicle’s battery has been disconnected for any
type of service or repair, the transmission will need to relearn the normal
shift strategy parameters, much like having to reset your radio stations
when your vehicle battery has been disconnected. The Adaptive
Transmission Strategy allows the transmission to relearn these operating
parameters. This learning process could take several transmission
upshifts and downshifts; during this learning process, slightly firmer
shifts may occur. After this learning process, normal shift feel and shift
scheduling will resume."
Perhaps disconnecting the battery for 15 minutes to "force" a relearning of the shift strategy might be worth a try? A bit of a long shot, but it's easy enough to do.
But remember, if you do this, it will have to relearn the idle as well, so don't be suprised if it idles poorly at first after you do this. Your manual has a simple proceedure to speed up the learing; however, if you just drive it it will re-learn the idle as well, it just might take it a bit longer.
Again, Ford Sez: "Because your vehicle’s engine is electronically controlled by a computer,
some control conditions are maintained by power from the battery. When
the battery is disconnected or a new battery is installed, the engine must
relearn its idle and fuel trim strategy for optimum driveability and
performance. To begin this process:
1. With the vehicle at a complete stop, set the parking brake.
2. Put the gearshift in P (Park) (automatic transaxle) or the neutral
position (manual transaxle), turn off all accessories and start the engine.
3. Run the engine until it reaches normal operating temperature.
4. Allow the engine to idle for at least one minute.
5. Turn the A/C on and allow the engine to idle for at least one minute.
6. Drive the vehicle to complete the relearning process.
• The vehicle may need to be driven 10 miles (16 km) or more to
relearn the idle and fuel trim strategy.
• If you do not allow the engine to relearn its idle trim, the idle
quality of your vehicle may be adversely affected until the idle
trim is eventually relearned.
When the battery is disconnected or a new battery installed, the
transmission must learn its adaptive strategy. As a result of this, the
transmission may shift firmly. This operation is considered normal and
will fully update transmission operation to its optimum shift feel.
If the battery has been disconnected or a new battery has been installed,
the clock and the preset radio stations must be reset once the battery is