I've run rD races solo, with another person, and in groups, and have enjoyed myself every time. What I like about going solo is you can really soak in the atmosphere on race day. It's electric! It's pretty incredible to look ahead of you at the hundreds (sometimes thousands) of people getting ready to cross the start line, and then turn around and see even more people just behind you! I love it. The only race that waiting around seemed like torture was this year's Frozen 5K. We got there extra early, and wound up going numb in the process. Eeek!