... unless you have to pass through that 'fur-ball' of AI aircraft which AIsmooth creates to get to your runway while on approach!!
Had it once approaching KATL where a jumble of some 30 AI aircraft must have thought i was the enemy (which in a sence i was: switched of the AI aircraft

) and kept coming at me like idiots.
None-the-less, AIsmooth MIGHT eleviate part of your problem. Try it and see... (it can be downloaded from Avsim.com for sure)
Andrew mentioned the upcoming ProFlight atc emulator. Ok, haven't seen the new version, but used the old one under FS2000 (i believe...) Was pretty legendary in those days. However, what ProFlight did not do is talk with AI planes. When it was not talking to you it started playing random pre-recorded atc chatter. So it could well be you are flying somewhere over Australia, when you hear an Danish ATR get landing clearance... Now if that isn't a worldrecord for long distance, i don't know!

Agree, MS ATC sucks big time. I am using RadarContact as ATC program. Has all the (IFR-)possibilities you could want, and more! Check it out on:
http://www.jdtllc.comInstead of FSnavigator (which has the disadvantage it can not be accessed without FS running), perhaps you can also have a look at FScommander? Does basically what FSnavigator does, but stand-alone. Check it on:
http://www.fscommander.comFor more advanced features i recommend FSbuild (my planner of choice.
http://www.fsbuild.com), but suppose when you have not yet used any flightplanner beside the (very limited!) FS one, FSbuilt could be a bit(!) overpowering...
Am sure you will work it all out in the end. Just keep on flying!

Have fun!
Stef