Cinema 4d is very well supported, but quite pricey. I use Lightwave 3d. Lightwave 11 is very stable from what I've heard, but Lightwave Mac support for plugin is really bad compared to the Windows version. I'm currently run Lightwave 9.6.1 under Snow Leopard with no big issues. Waiting to see what Apple does with the Mac Pro, before upgrading to 11. I may have to switch to Windows if we don't see a new Pro soon!
Yes, I have tried Modo. I liked everything about it except the shader tree. I found it to be very clumsy, and if you have a lot of surfaces, it get to be a bit of a mess. Lighwaves shading system is much cleaner, and easier to deal with. All around I think Lightwave is an excellent deal. It's the workhorse of 3d apps including everything in one package at one cost.