Coming into US from Canada w/ > $10,000 -- problems?

[teddyFBI]

So I went to my bank up here in Canada to fund myself for my upcoming WSOP trip and the branch manager, after hearing how much $ i wanted to withdraw, warned me that a lot of clients who were carrying that much in either cash or traveler's checks into the US had been not only questioned but actually detained for HOURS at customs.

I told him i was pretty sure that it wasn't a big deal as long as I declared it and told them why I was carrying so much (my plane ticket to Vegas should explain a lot). ANyone have first-hand experience with explaining to customs > $10K? Is it just a quick Q+A or will they actually give me a hard time about it...?