I purchased the ZX-1 RTR as it was my first buggy and as razzor said it has been a great vehicle to learn on. As my driving got better i started hopping the parts up one by one and now there is hardly any RTR features left on it(aside from the suspension arms). It is now a fully blown pro version. The only plastic on it are the suspension arms and wing mount and the rest is alloy with a nice knife edged radio tray and centre diff mounts.
I've also heard caster is bringing out a brushless buggy soon.......should be very interesting