Pam, buy it! It is well worth the money. It is so much smoother! And the visuals, especially the skies, as others have mentioned. It handles higher settings much better, although I still have to reduce some of them to keep the sim from freezing or ctd'ing. Doesn't take long to find the causes in the settings. Reducing them from max, one at a time, small steps fixed 90% of mine. I can run much higher than even in v4.5. FSX? Never load it anymore, 10 times buggier and nowhere near as smooth. As for your aircraft, if they are FSX Native, and have .xml gauges, along with a 64bit sound gauge/module, they all seem to work well. Watching the "compatible testing" thread, it seems quite a few that did not work right in V4 are working again in V5. (Still waiting on MilVis, and TacPac tho'.) Haven't had to pay for an upgrade from V4 on any aircraft, yet. It was the FSX/V1,2,3 upgrades to V4 (32bit to 64 bit) that were the costly upgrades on the more complex aircraft. A2A, MilVis ADVanced, and VRS F-18 and TacPac, that cost the most.
I have the new ORBX True Earth Washington State, and it is BEAUTIFUL! They upgraded 98% of the default airports in the state, as well as adding some not in default! They hinted in some posts, that Oregon is next.
An 8GB video card is a must. If you need help with the purchase, I will be more than happy to help out a fellow VETERAN! Just let us know.