'02 ZX5 Hard Shifting

Two years ago I bought a used '02 Focus ZX5 (automatic) from my local Ford Dealership. The car had relatively low mileage, looked good and ran well with one minor exception. About 6weeks after I'd bought the car, conveniently 2weeks passed the 30day lemon law, it began to occasionally experience a noticeable hard shift, well at that time it wasn't real hard but enough to make me notice. I spoke to the dealership and was told, well it's near the first major checkpoint (mileage-wise) so bring it in and we'll do a diagnostic and all the other stuff that comes with their maintenance schedule .. and it would be, at the minimum, $600.00. Well needless to say since I'd already had the other stuff done elsewhere (oil change, air filter, tires rotated, etc) and all I really wanted was the tranny check, I sorta just let it go.

In hindsight, not such a good idea. Now two years later it has gone from being something I notice, to something I dread. It doesn't do it all the time but occasionally it will pull a real hard shift to the point that you are actually bounced in your seat and it's gotten more reluctant to shift at all, at times revving up to 3000 to 4000 RPMs before shifting.

Does anyone know if this is a common issue with the Focus, particularly the '02 model, and if so, what did it take to set it right? The local transmission shop says it could be anything from a speed sensor going bad to the biggie, clutch/transmission rebuild/fix, and on a 5yr old car, there's only so much I will invest as opposed to simply getting rid of it.

Any help/suggestions would be greatly appreciated .. thank you in advance!

Erina