FFXI was my first real MMO that I spent any time on. I played all the way to the endgame at the time (Sky), and was in the top NA guild (Machina) on Asura. I quit just after CoP came out.

AoC is far less linear than FFXI, as FFXI basically trapped you in the zones around your starting city. In AoC the newbie area is fairly linear, and once you leave there you have several directions you can go in order to quest and level/explore without getting totally beat down.

As for solo vs. group play, I'm probably biased because I tend to solo as much as I can in a game :P. However, you're neither forced to solo nor are you forced to group (except maybe for harder quests). You can easily advance by going out and doing things yourself, or by getting some friends together and doing stuff as a group. Periodically people as in the OOC (general chat) channel will ask if people are doing quest X or Y, but it's nowhere near like FFXI where you basically were forced to group post level 10 or else you don't advance at all. As for the XP in grouping, it kinda looks to me like you get XP based simply off of the level of mob you're fighting, and it's not split up or bonused by being in a group.

The environments and towns feel more "real" than in either FFXI or WoW, I believe simply because of the graphics. It's not just a wide path with things painted in on the sides, it actually feels like you're inside whatever place you happen to be in. Think Sand'Oria or Windhurst, but with the feeling multiplied by about 3-5x and you have the feeling of an AoC town. For the outside world, check this out:

[media]http://www.skemp.net/images/aoc/Fenwick_picture005.png[/media]

That is a screenshot of Connall Valley. I'm up on top of a huge mountain, and you're seeing probably 1/5 to 1/6 of the zone there. The place is huge and real-feeling.

If you liked how FFXI really basically made you stay on the path from point A to B to C, with only a little option for variation, AoC might not be for you. I personally was a die-hard FFXI person, but I still liked it moving to other MMO's where I had more freedom and didn't need to sit around for 3 hours waiting for a group that lasted 30min. :P Aside from the $50, you don't have much to lose for trying, but I'd say poke around a bit more and follow what your gut feeling is after.