I have used the ADuC834 and I generally like it. If you need high speed data aquisition, the Cygnal or Dallas Semi parts have faster clock speeds and therefore can process data faster

The important feature for 'beginning' is ISP (in system programming).
Cygnal has it as does most new Philips and Atmel derivatives. I know that Dallas is behind on this one and someone need to state if the ADuC is ISP.

Other things to consider is internal RAM (if you have enough internal RAM and Flash you can have a fully functioning board with 3 chips ('51 derivative, Max232, and LM2905). If someone is trying to tell you about 8255, external code EEprom and such, close your ears.

Erik