I have an MSI Wind running 10.5.6 flawlessly, except for the microphone for iChat.
But, I have a Mini set to arrive in a few days and a 32gb runcore on order and will do the transition to OS X when it all comes together. I like the Wind for the size of the HD (160gb, standard 2.5-inch SATA) but prefer the Mini's design, which is why I want to give it a try - that and the FULL function in OS X. I'm not so sure of keyboard size and screen size, but will determine that when I can compare them side by side.
That said, the install of OS X on the Wind was not difficult, but it did require a lot of little tweaks. Battery life on the Wind is weak with the standard 3-cell battery (maybe two hours) and with the Dell I'm hoping for better battery life and iChat function.