Comparing linux and windows is liking comparing apples and pears. Ok, they are both fruit and sometimes it's hard to tell the difference, but their flavor is really different.
Considering install time, when you do a minimal install (just basic X and drivers) I don't think linux is more time consuming than windows (if you're not having any kind of exotic hardware).
Most of the time your system will already install office and a vast amount of other apps for you (which consumes some install time). The only time remaining for you to complete your install is to configuring your X, sound, ... At windows, you get a bare install (unless you use wordpad as textwriter and your users stick to patience and minesweeper). At this point the misery begins: installing drivers, all the other apps (including office), online updating, ... luckily my good friend bill has include a nice automatic update (into a webbrowser, isn't this just asking for problems?) which download all the packages while I'm using the machine (causing my game to lag and my fps dropping down) and even more: everytime I download a small set of critical updates a nice popup appears stating "rebooting your machine is necessary to complete this update". Sometimes this rebooting will even happen automatically. Finally after downloading about 500mb of updates and rebooting 20 times my machine is ready for the action... So don't get me started about install times
So the machine is working, at least, for the next few months: The only windows machine on my network has a wireless usb connection and guess what: only users with admin rights can use the network card, so everybody working on that machine can freely install software, make system critical updates... leaving me with the job of reinstalling it every sixth month because control is lost to spyware... On the other hand I have a box running debian and allowing me to surf the internet, chat with my friends, post on forums, enjoy the sound of a mp3 and this machine has been running for 3 years now and from time to time apt-get updating and upgrading is helping to keep it fit, probably for the rest of its days untill the mighty computer-Lord takes out the soul of it's harddrive or cpu-fan. Compared to reinstall times, system crashes... I must say, you don't loose that much time by installing linux
Well, I probably can talk about performance, money and to me the most important issue: user access restriction, but that would result in a 6 page paper full of flame against m$ (and according to forumrules, you have to behave decently around here, I suppose) and it's not my intension to persuade die-hard windows users by pointing out the the advantages of linux
Well to put it all together: my personal opinion is users are freely to use the software they choose (even if it's windows), that's what linux is all about: freedom of choice. Windows has its advantages, linux has advantages (but they will become more clearly if you adapt a linux-way of thinking and managing your system). The only thing I don't understand is why people are ranking the value of a DESKTOP system by its install time...