same here. I think after the Radeon X series and GeForce 6 series came out, there's been a new standard for graphics in a lotta games, and NL isn't quite there yet.
We are currently even further in graphics with the Radeon X1 series and the Geforce 7 series [;)]. Also, No Limits is awesome where it is now because it can be run on even a real crappy computer without the simulator running or looking like crap. On the other hand, I can max out every detail, including AA, and my 7900GT holds out at around 30 FPS on some of the heaviest files! So I think that currently it's pretty versatile, and when 1.6 is released, that will probably increase the graphical demand slightly, as did 1.5.
Ack, I'm still stuck on a radeon 9600pro 256mb, but I don't have a PCI-e slot so there's not that much I can do to upgrade.
I'm running No Limits on a Powerbook G4 (1.0Ghz, 1Gb RAM, Radeon 64Mb 9600 (400/300), and I can run it at my normal resolution with everything on high (except for AA and some reflections and such) and get steady performance, so that Radeon 9600 256Mb must get better performance, I'd think. Try OCing the card too, that always helps.