Pda. personal digital itance.?

i was wondering if anyone knew of a good pda(personal digital istance). i want to buy one but last time i bought one it didnt even work very well, the pen wasnt working with the screen. i want a brand and/or a model number of one that you have had personal experience with(oops i want, well it would be nice to have). so can you let me know if you know of any good brand and or models.