I think Im one of these people who prefer going out alone....I have one or two other people I know who into running/fitness, and I found if I go with one of them, I feel Im either holding them back or I struggle to keep up and that makes me feel worse...OOOOOORRRR....if I go out with my other half or one of my other friends...they take more breaks and I lose momentum so to speak and either feel like I havent got enough from my run, or get bored of walking and feel guilty they are out of breath...
I know everybody is different, but one of the reasons I got into running was because I liked to have that time on my own where I dont feel like anybody is comparing theirselves to me, that and the gym was getting expensive, and although I had my own equipment in my garage, it did get a bit stuffy in there at times....let alone boring repetative.
Anyways....I know most people prefer running with someone else...and Im probably just weird....but I feel I preform better when Im in my own little world with my ipod on, singing away to myself, I might get funny looks for all I know....but, I dont even notice them, Im too lost in my own little world!