hi again
thanks again for the advice
can i ask : if i go for the Diecimila, will it be able to support maybe 8 or 10 of the PING))) Ultrasonic Sensors or the SRF08 - High Performance Ultrasonic Range Finders, for example.
if so, then i think i will get started with a Diecimila and one sensor and begin my learning from there as it sounds like i have plenty way to go yet. 
any other hints and tips most welcome