I prefer 7 speeds. The cassettes last longer because the cogs are thicker. The rear wheels are stronger because they have less dish. None of my bikes has more than 7 speeds. I can get the parts cheap because most people want the "latest thing". Seven speed shifters are somewhat hard to find, but that's not a problem because 8 speed shifters work just fine.
Here's the mixte I just finished building for my wife:
It's all 7 speed Shimano 600 with 8 speed Ultegra 8 speed bar end shifters converted to thumb shifters. Almost all of the parts on it are used.