It got pretty cold overnight - I have a 15 degree rated sleeping bag (Marmot) and had to get fairly well bundled up to stay warm - the ThermaRest was crucial! I'm not sure exactly how cold it got (was too huddled in sleeping bag to check temp

) but the condensation on the tent was frozen when we woke up in the morning at around five.
As for the conditions on the summit day, it varied quite wildly during the approach so that layering is a must. When we left at about six AM I had two shirts, a sweatshirt and gloves, and was wearing plain nylon backpacking pants. By the time we reached trail crest the sun was shining warmly and I layered down to just one shirt, which was fine until the summit. Once at the summit, when we relaxed a bit and body heat lessened, it got a bit chilly and windy and so I layered back up

It never got to be what I would consider cold, but you definitely want something to protect from the wind at the top. My two hiking partners wore heavier jackets and pants, and they were comfortable, but I was quite comfortable in the sweatshirt and thin nylon pants. I think it depends on how "hot" you normally get when you're hiking. I have a fairly high tolerance for cold.
The only thing I would have done differently is brought some thicker, waterproof pants - the glissade down soaked and numbed my backside! THAT was cold. Both my climbing partners wore waterproof pants and I think they enjoyed their glissade considerably more.
Also, keep in mind that the sun was shining the entire time on our summit hike. I can imagine it getting cold very quickly if the clouds rolled in, and I probably would have wanted a heavier jacket in that case.
You dont know how good it is to get this first hand info!! I sure you felt the same last week wondering what to expect. I want to thank you for the valuable information and details.No problem at all. I was VERY apprehensive about our trip, because I have a lifelong fear of falling to my death off a mountain, so this website was a godsend in the weeks leading up to our adventure. I'm happy to return the favor. Of course I probably spent more time finding scary pictures and frightening myself than I did finding reassuring information, but nevermind
Also, I'm glad you find my advice useful - keep in mind as you read it that I am a relative newcomer to this, and take my impressions as such. Have fun and BE CAREFUL!