Hi BRL,
I a a PPL student (have 10 hours) and use Microsoft Flight Sim 2002. I find FS a very useful tool to my training and a lot of fun. I have purchased an excellent model of the C152, my training mount, and it is a very good representation of the real thing from the handling point of view. I find it very useful to be able to practice running through checklists both on the ground and the air using FS and the plane I use repsonds as Id expect! Furthermore the wealth of excellent add on scenery makes it possible to simulate very accurately the airfields, local scenery and terrain you regularly fly around in for real. Products like Just Flight's VFR Scenery, VFR Terrain and British Airports series all greatly enhance the FS experience and make it much more fun and realistic for me from a learning and practice point of view. There is also many free addons from sites like
www.avsim.com that enhance the realism and fun of FS.
I personally have not used X Flight but i hear the flight dynamics are excellent but the "overall" package from user friendliness, scenery, graphics etc ae not the same as FS.Both xplane and FS have strong supporters and it all depends on what you want from your flight sim and personal preference to what you prefer.
Overall, I find FS really good fun to play with and use and personally find it a useful tool to aid my real world learning. Its also a great fall back when you are desparate to fly but the weather and/or money get in the way but obviously is not a patch on the real thing!
Hope this helps!
Fingers