The default settings were very low on my system, but I left them there for the missions -- landing at St Maarten was a steady 20FPS, and went like clockwork -- actually better impression of speed, distance and approach than with FS2004.
The water is the thing I noticed most -- the water effects range from brilliant to strange. The impression of tropical water is marvelous, but i hope that the same bright water isn't everywhere -- as I look out the window here at Lyttelton the harbour is very drab and milky, so I'd be interested in seeing how FSX handles it.
I then turned the graphics up to mid-high, and did some low-level cruising about in the trike. This is a cute little thing, real easy to fly:)
Again, the water really makes an impression:

But the land textures are variable at best. I think its the difference between the stunning water and the not-so-stunning ground that really shows it up. The autogen trees are perfect, but the buildings are, well, so 2004...
With the graphics turned up I was sitting at around 5FPS, which wasn't all that great, but flyable in the trike. Returning to the airport FPS dropped to less than one, which pretty much brought the thing to a standstill, although I could esc -- end flight to get out of it.




