I don't know why you wouldn't... You can get instant gratification either way. Download the trial and plug in the serial when the box gets there... I don't think it'll take longer than 30 days.
I bought the boxed version and it came in two days (standard shipping). I like the idea of getting a manual even though I can access the on-line tutorials. Unfortunately, I have not been happy with the application performance. I am getting the spinning beach ball and freezes all the time. I have plenty of ram and HDD space. I only have 3,300 pics in my Library. Major let down unless fixes soon.