I've been training alone for about the last 1 1/2 - 2 years, but I think there is something to be said for a solid partner. When I started lifting, I knew nothing. My buddy Enigma got me into it, and taught me tons. He educated me about supplements, and thanks to him, I didn't have to go through the stereotypical first cycle of fake gear. It's hard to find a good partner that motivates you, shares knowledge and pushes you that extra little bit, without screwing up your routine. But I moved away about a year ago, and have been lifting alone since. I like lifting alone most of the time, but sometimes it'd be nice to have someone to kick you in the ass when you're slowing down.