Modo is a great alternative program for Arch-Viz. I switched 3 years ago and I have enjoyed watching it develope. The selections tools alone make this program a very efficient and powerfull one. It doesn't have a particles system nor CA tools right now but it is great for the everyday job. We might see some of those tools in the 401 release. Luxology has a very strong and helpful community. The developers are always answering questions and helping the users with any issues they encounter which is sweet. Also, make sure to check Luxology TV:
http://www.luxology.com/training/
IMHO, it is by far the best training resource I have seen for any 3D application (C4D just lunched something similar). Right now, Luxology is offering a 30 day trial version of Modo for the Skuuma Furniture Design Competition. It comes with some extra goodies. There is no reason why anybody shouldn't give it a try
http://www.luxology.com/skuuma/
Here are the Arch-Viz galleries:
http://www.luxology.com/gallery/imag...=Category&id=3
http://www.luxology.com/gallery/imag...=Category&id=4