For non tourney games they would be fine, I use mixed Non and
GW bitz in a lot of my armies. Some tourneys the mini has to have a certain percentage of
GW, check the packs for details to prevent dissapointment.
Have a look at Hasslefree, West Wind, Old Crow, Barrule (Aniteoniti's workshop) and TheBaggageTrain (on ebay) for more vehicles and goodness. You can also look at collector type models, as I've seen WALL-E's converted into 'Kans and I've used Halo Warthogs as Recce vehicles