I switched from a PC to Mac a year ago.
Thus far the PROS:
For the most part, the Mac is a much better machine. It boots up much
faster and not having to worry about viruses and spyware is great.
It is awkward transition at first but you will figure it out after
spending a few days on the Mac. I find windows to be very clunky now.
Also the applications flow together really well. Macs really just
seem to work better than PCs.
I have found that moving documents back and forth is not a problem. I
recently used Power Point (2008 version) on my Mac to make a poster
and a talk. I had to use a PC to present the talk and print the
poster and both converted perfectly. I think some of the conversion
problems were fixed with the new Office (2008).
CONS:
The biggest negative is that there are a lot of important programs
that do not run on Mac (Access, PopTools, SAS, GIS, Canvas).
I use Parallels to run Windows and it works great. However, this adds
to the cost of the computer as you will have to buy both the software
and Windows. Also, it takes up memory and hard drive space.
If something goes awry (less likely to happen on Mac) you will have
to find a "Mac-certified" technician to fix it. This can be a big
problem if you do not live in an urban area. Also, Macs are harder to
fix yourself.
This may be a coincidence, but three of my colleagues and myself
bought Mac laptops in the last year and three of us had our hard
drives crash. We lost everything that was not backed-up.
OVERALL
I think I would buy a PC if I had to do it over again. You could
purchase quite a nice PC for the money you would spend on the Mac.
The biggest reason for me is the programs that only work on Windows.
If you will be on Windows the vast majority of the time I would stick
with a PC.
Hope that helps.
Dan