The download took me about 1.5 hours to download, backup, and install/update. It took way too long for not being able to observe any obvious new improvements. The most disappointing part is that many people likely did this at times of the day that inconvenienced them. For me, I began the update just before I went to lunch, and when I came back, it was only halfway done. The consequence - I was without my phone during lunch, and my phone was essentially out of commission for the second 45 minutes, which means that I could not receive nor make calls in the middle of the day. Apple could have at least released a message saying "This update will take 1.5 to 2 hours and there isn't really anything new."
update: the actual downloading part took about 20 minutes.