Multiplayer Battling in Solo RPGs

Do you enjoy playing with a friend in games designed for solo-play? Examples I'm thinking of are Namco's Tales series (or even FFVI/IX's optional use for two controllers, despite being hardly useful).

I think it's loads of fun actually! Even in the Tales games where the AI is great, having a friend play a supporting character in a fight can really allow for more strategious play. I don't get the chance too often, but when someone video game literate is around, I tend to chuck a controller at them for kicks. :D

Back in the day me and my one friend were racing to beat FFIX and we would bring our saves over eachother's houses and play the game, i thought it was incredibly fun back then. More recently I played through the game with my one college buddy and it's still pretty good.

Demon's Souls is a different matter. I'm not sure if it's really designed for solo play or if the multiplayer was integral from the start, but for some reason I shy away from the online play in that game. I did play with someone who invaded my game as a black phantom that didn't attack me and helped me along, it was pretty cool, but I just don't bother to use the option to invite the people around into my game. I can't put my finger on why...

I thought it was so cool to have it in IX but my brother would never play with me :(

My friend is coming over this weekend to play Arkham Asylum with me! I played through Resident Evil 5 with my brother-in-law. Good times.

I liked playing Tales games or Eternal Sonata with friends, but those have action elements to their battle systems. If it were just a turn-based system, I'd find it kind of boring.