well I haven't had any problems with Poser 5 ... I haven't used it a huge amount as I'm easing into it gradually like :) Its a sensible upgrade from Poser 4 for an advanced user. The key differences: dynamic cloth, dynamic hair (fiddly as heck), volumetric lighting, procedural materials, and an improved library management. The downsides? takes a strong system to use it, the new figures are eh and the Faceroom only works with them, the firefly renderer is sloooooow and the new material setup means that some older poser files need to be fiddled with before they render properly.