OK ... here are some results of my "tests". Not so much as a *performance* comparison (as my Vista FSX is so loaded withaircraft and tweaks) - more of a general "what if".
Win7:
1) Checked that my PC was 64-bit capable.
2) Bought a completely new HD and (temporarily) disconnected my current HD's. I really didn't want to mess up my current setup.
3) Installed the latest 64-bit RC (thanks, Doug!) ... with activation key from the Microsoft site.
4) Installation was pretty quick and absolutely painless. You do NOT need a prior XP or Vista install.
5) Disabled UAC (user access control).
FSX:
1) Installed and added both service packs. Did not bother to install Acceleration (which I do have on my Vista FSX).
2) Not enough control over graphics settings, so I installed nHancer. NOTE: In FSX I had to actually tick "anti-aliasing" for the nHAncer AA settings to work. I didn't have to do this with Vista 32-bit.
3) Installing scnery is a mission. I think there'll be another thread on this, as Doug and I found different ways of doing it. It's possible, but requires some very "un-intuitive" procedures!
4) Installed a couple of aircraft. No problems.
5) Copied all my WOAI files over (via a 3rd PC or memory stick) and disabled the default AI by renaming the traffic bgl.
So ... the end result?
Windows7 does appear to be an improvement on Vista (which I have to say I loathe). Other than install FSX, though, I can hardly say I've tested it. It found my network, my printers and all over devices with no problem. Have yet to see whether it will co-exist with my D-Link WiFi hub - which Vista absolutely did NOT. Generally, I like it. It inspires confidence (like WinXP) instead of that "what's going to happen next" feeling that I keep getting with Vista. You feel in control - as opposed to fighting with the O/S. Not very scientific, this - but you get the picture

Other than loading times, I can't say I've seen a huge improvement in performance in FSX. It does appear to be more stable, with maybe fewer graphics artefacts. Could be because Win7 memory management is better. I'm also comparing a 64-bit system to my old 32-bit. I tried DX10 preview - which worked OK, but I disabled it as all the WOAI models aren't compatible and there are odd issues with some or Rob's older sceneries (notably AKL, which is an FS9 port-over).
Here are some piccies (NZWN) of a pretty well default install - with (working) WOAI and all of Rob's sceneries installed:


Thanks to Doug - for the ISO's and general encouragement
