I certainly more comfy playing in Single Player, I just feel awkward when people are watching my every move (not really) but it does restrict my freedom.
I'm kinda like the "Anti-Troll" I am the type of guy who would at all cost, avoid pissing off other players as I feel it would bite me in the ass later. I'm that ultra conservative player everyone makes fun of, that's why when I play multiplayer, I tend to avoid the other players like a plague.
I played GTA Online, in freeroam I avoid other players but when I do jobs with other players, it is kinda fun I enjoy it, but with my personality its obvious that I am not much of a multiplayer guy, so I have no knowledge weather GTA Online is a good multiplayer game or not.
But TL:DR. I'm not the guy to ask (makes my wonder why I am commenting at all) but GTA Online is certainly still worth the extra development cost and time. It isn't just a tacked on multiplayer mode for the kiddies to enjoy, it is deep and very well developed. It may have a few connection issues, a few bugs. But thats just due to the amount of people playing it.
To think something as well made as this is bundled up with the (in my opinion) the greatest GTA game ever and that 60$ you paid for it pails in comparison to the content you are receiving.