I liked EDTASM for the TRS80. But TRS Basic Level II was amazing because it was so accessible in the days when practically anybody could write a program that delivered business advantage. IMHO one of the key features of those times that is only being regained today was the "firmware OS and language" that allowed a machine to boot quickly and run programs without fail. But the TRS80's 48K RAM limit began to make a difference, Amiga and Amstrad briefly sparkled with better screens and resources and cheap PC clones began to appear with hard drives, so that was that.

If I were starting again in 2010 I'd be doing something that works on a phone. Choice between Android, Windows Phone and one of the Palm OS I guess, versus Cloud/browser-based stuff. Though I'd also look carefully at the generic OS coming out of China- I had a $50 phone sent from China with a GUI that is indistinguishable from the iPhone, running on a Chinese OS. Probably go for Cloud so only the GUI needs to be loaded locally, preferably by browser. I believe I would take particular notice of MS's recent announcement of a new "clean break" Windows Phone 7 version that will be incompatible with V6.5 and previous, rendering current apps obsolete...