If you're used to Bryce, then try to get a free copy of Amorphium 1.0. I've had it a couple of days and its similarity to Bryce is astonishing! I'm not sure how good it is for modeling accurate, hard-lined shapes, but for anything organic it's excellent. It is free with the latest edition of PC Format magazine. If you get it and have difficulty installing it, I can help you out with patches, etc.