Your system will run it, BUT. Whether you are happy with how it runs no one else can say. I have an I7 clocked at 3.5Ghz, 6GB of RAM and a 756MB NVidia 275 graphics card. Not a bad llittle system and I can finally say I am happy with how it runs FSX. It is very person dependant and I like it to look _really_ good and be very smooth!
I think the graphics card on you system might let it down a bit however FS is CPU limited, not video card limited so a fast processor is way more important than a fast video card.
As for what you can get out of it. With decent add-on aircraft you can have very good flight physics under normal operations. Some have OK stall and spin behaviour and recovery but they feel nothing like the real thing. It is fantastic for practicing the procedural aspects although I must say, the freeware Eurostar for FSX was a great plane for practising my circuits and navs, it really felt a lot like the Sportstar I was flying at the time. I am a slow learner and the sim did help.
A MUST have to get the full benefit is Track IR head tracking, this is so the view on the screen moves as your head moves. Rudder peddles are also very high on the list too of course!
If you do get FSX then I would suggest you get the scenery from Orbx (demo available) and the airfields from OzX (free). Also, turn off AI aircraft and fly on cloudless days. AI traffic and clouds really hurt low and mid power systems.
Steven.