I have an older CoolscanIV. Think I bought it in 2003 and although it does not get a heavy hammering it has been fine.
I use Nikons own software which is fine and not difficult to use, I believe it will work with Win XP and 7 and certainly works with OS X Snow Lepoard 64bit.
FC2 is right in the fact that if it did go wrong you might run into problems getting it fixed, but to be honest it is more software issues that you will encounter, Nikon software is not the best I have ever used but for me better than Silverfast or View Scan(?).
The IV will only go to 2900dpi where as the V will go to 5000dpi. They will certainly get all the details out of the neg/slide your after and they have the ability to create custom profiles for the various film types.