A friend of mine is a Modo user. He loves it, and Lightwave users should feel fairly at home inside it. I use Maya mostly, but also use Houdini sometimes for effects and particles, and have been using ZBrush more often lately. I'm hoping that there is a way to use normal maps inside jitter to fake detail, but from what I hear about Modo, I only hear good things, especially from Lightwave users.
If you want painting abilities for modelling, you should look at ZBrush (pixologic.com) or Mudbox (Autodesk). Mudbox has a more intuitive interface, but personally I think ZBrush is much more powerful for modelling and detailing. I'm pretty sure that only these two applications will give you the control that you really want in a "brush" based modelling/painting package.
WinXP, 1gig ram, nVidia FX3000 card (256megs vram), and i work on 2 million polygons on screen pretty close to real time in ZBrush.
I'm pretty sure that my Macbook (2.4Ghz dualcore, 2 gigs ram) would be able to do at least 5 or 6 million polygons (They don't have a UB-OXS version of 3.1 yet).