I love running for a group. My prefered size is 3 players plus me, the GM. However, after moving to a new city two years ago me and my fiance didn't at first have time to find a new group. I began running a solo campaign for her in the meantime, and it went really well. Since then, we have come to enjoy it so much that we haven't yet gotten around to finding that new group to play with.
In fact, when we did go to the FLGS to check the postings on the wall (we had had bad luck with finding players on the internet in the past, and so stayed away from that method) we realized that maybe we didn't *want* to find a group. We looked around at the people playing in the store and realized we didn't want most of them in our living room for several hours a couple times a week.
Don't get me wrong...I'm not a snob...but we saw how different our playing style was from the norm and couldn't bring ourselves to try and find new players that would suit our "group". So, now we just run solo campaigns for each other and leave it at that. Our old group was too close to our hearts I guess to find a new one to build new bad-ass-gaming-memories with.
On the upside all the solo campaigns have been really great, and I've recently come back into contact with most of the members of my original group from before I even met my fiance; all of whom are interested in getting back into the hobby now that they know I live in the same city as them, and am willing to run a campaign. However I don't think the group we had before we moved here will ever be topped, even by the veteran crew I'm going to be running for soon...and nothing will ever come close to the solo campaigns I have run for her (and vice versa).
I suppose it's due to the depth of personal story that a solo campaign allows for...it's hard to touch that in a group environment. What's everyone elses experience with solo campaigns?