They truely are! And I own/compete w/ several different breeds.
I think that if you're a disiplined dog owner and can make corrections as needed and give praise when needed- a nice balance, then you shouldn't have any issues! The Yorkshire Terrier is just that- a TERRIER, there is a toy side, but overall I think that fiesty steriotypical attitude is in all of our Yorkies, or at least it should be.
Loads of play and in doing so, teach him the rules of engagement. In all honesty, I think that you'll be very pleased w/ your new fur baby assuming he's healthy, because the Yorkie temperment/manarisims is just the best- VERY rewarding! Just like my signature says: Big things come in small packages!
I'd consider you begin looking into training facilities in your area now, before you get your kid. That way if issues arise, you're not alone! And you've always got us here on YT!!
~Leslie
One more thing- PHOTOS!?!?!