I don't know about everyone else, but Carrara6 impressed the heck out of me.  It does things Truespace doesn't even attempt for less than the price of Truespace's plug-in renderer.  I'm sure that XSI is probably better in every way than Carrara, but I am (at least until the month's end) comparing a $200 program to a $2000 one here.  The new hair looks great, but I'm really stoked about those atmospheres, displacement modeling, and oh yeah, COLLADA export.

But it still doesn't have Truespace's awesome realtime "photoreal" workspace.  I hope they're planning that for version 7.