PowerPC machines were falling behind overall. The intel towers were faster with twice the drive bays, although I think the G5s had more internal bandwidth in terms of PCI lanes. Some companies were slow to port things to intel build, but around 2007 and on PowerPC releases were drying up. By 2008 almost nothing new was released for PowerPC era machines. Support evaporated rather quickly, especially as many of these machines were sold as new during the first half of 2006. It seems like people misinterpret Apple's focus shifts as being tied to their move to intel. Developer support has actually improved in some ways since the move to intel. I can't see many downsides, and when people claim that late PowerPC era software was well optimized for the platform, I have to assume they never used anything beyond iphoto.