David Gwynne (dlg on #opensolaris) has created a very nice driver for LSI MegaRaid SAS controllers. You can find it here.
I have not got any hardware, so I've not tested it, but this driver is the model of simplicity and elegance for an HBA, from what I can tell, weighing in at only 1500 lines. A great deal of that is no doubt thanks to the simple model of the hardware, but the simplicity and elegance in the driver should be credited to David as well.
I'd like to sponsor this myself for integration into Nevada, but I haven't got any hardware. If you have hardware to loan for qualification testing, give me a shout, because this looks like a prime candidate for a Nevada integration.