I have just installed an XP upgrade. It is very easy although it takes nearly two hours to complete. It was my very first upgrade hence I am not certain if it is quick or not exactly so.
Word of warning though for those who upgrade from Windows Me. I have discovered that it is much easier to reload my computer and start reloading the rest of the software afresh than just to install the upgrade. Although the upgrade worked as such I needed to update most of the drivers for my printer, broadband connection etc. Reload seemed to be an easier option in the long run.
There was one more glitch in the system. After the upgrade my computer refused to switch itself off automatically. I contacted Microsoft UK and a solution was offered (Control Panel, Power Option, APM, enable APM support). They diagnosed the problem and offered a solution really quickly. Great customer service.
As to the Amazon' service: I placed an order, I was kept informed about the progress, they delivered on the day indicated. Judging by my past experiences it is pretty much standard. I would highly recommend them as well.