Sprite: there's no noticable slow downs from ROS 4->Select, and some areas of Select are faster than OS4 - that's just my observation and from docs I've read, plus I haven't seen anyone complain about things running slower on the support mailing list.
Milton also said, "I didn't see any real features which would make a non-Select user want to buy this version" - what, other than the previous three years of Select features?