Just to give you an idea how quick the process works, I just bought a book from Borders and opened the ACSM file in ADE (this stores the file on my computer.)
I then cut the ebook and pasted it where I keep my ebook files (because I don't like to store data on my C drive... which is the only option ADE allows.) This takes but seconds to do and is not required, but is part of my workflow.
I then opened calibre and used the add books button to bring the ebook into calibre. This happened almost as quickly as it took to click on the button. I then used the Connect/share button to convert and email the ebook to my K3 which took 1:33.
For the record I'm using Win7/64 on an old Core2duo E6600 I built 4 years ago running 6 Gigs ram with an 80 GB SSD for the OS and a 320Gb 7200 rpm (gettin' full!) data drive. This is hardly state-of-the-art hardware.