For me, it's solo. I like to ride with friends at the rallies I go to but generally, it's alone.
When you think about it, you're basically alone even when you ride with someone. You don't/can't talk and your on your own bike so what's the diff really? I used to ride with Dave(Roadworthy) every Thursday for a couple years but that has faded away and we don't go out on the bikes much anymore. I don't mind riding with a bud or two but I just head out on my own 99% of the time. I have a 1 and a 4 year old at home too so my wife is never with me either...which is FINE by me.