1. The author has seen good and bad...but when it's bad it's really bad.
2. It's all about the accessories. Differentiate with ties, bow ties, socks, pocket squares, etc. Like Unbelragazzo said, sticking with white shirts may be best. Most of the pictures in the article seem to work off a white shirt.
It's one thing to mix and match with your groomsmen, but don't forget about coordinating them with the bridesmaids as well. Imagine how it will look in a photo with the ENTIRE bridal party in it. Will it look cohesive? Or just appear as if nicely dressed people were pulled off the street. When you've both agreed on a primary color theme for the wedding perhaps work the outfits around that color and allow for some complementary colors in the accessories.
Best of luck to you.