I'm an ex-WoW player, have been playing now for about a month or so, and love it. Once you get out to the ML, the missions become much less specific to certian skill trees. I have yet to find a "class" specific mission which will award XP and items like the ones you get from the four NPC's in noobie isle. There are a few chains that are rather involved with the main plotline of the game, but overall, it's just faction grinding repeatables (getting to the rep you need is much less of a grind here than it is in WoW thankfully). Of course, I haven't yet gotten to the proper rep to swear fealty to Kami or become a Fyros citizen (for lack of trying.. I only started this weekend, and am nearly there already). There very well may be many more new and interesting missions to go on after that.
The mob behavior and spawn style is a bit different on the mainland. For example Bodocs, which are social animals, will become aggresive and attack you if you are attacking another one nearby. With the spawn style, once you've killed one creature, be prepared for two to three more to show up soon. That can make solo hunting aggresive creatures a very dangerous proposition.
There are many teleport spots on the mainland, and tons of area to explore. You can spend hours just running about and dying while trying to figure out which critters are aggresive and which aren't.
Also, be advised that if you have friends playing with you on the island, each race goes to a different home city when they go to the ML, and to get to one of the other cities you will have to run it the first time (once you've been there, you can teleport afterward), and pass through very dangerous lands with many big nasty creatures. Getting an escort from higher level players is a must to make one of these treks, although if you ask around a bit, I've found that many people are very helpfull.
Other than that, it's really not so different from what happens on the island... you gain XP in the skills you use, you can spend hours playing, or just a few minutes working on one of your lower-level skills and get visible results. You can get together a group and go hunting for higher level critters or go searching for a boss mob. You can get together with a friend and switch off who's healing and who's killing, or you can go XP hunting solo. You can farm easy to kill lower level critters for crafting mats or money. You can scout around for a good prospecting spot, and just dig in the dirt till the resources are depleted. It's a very open-ended playstyle. There's plenty of things to do and many challenges to be had if you play 30 hours a week, and there's plenty of things to do and progress to be made if you play 5 hours a week.
In short, Ryzom is what WoW promised to be without ever delivering... both casual and hardcore friendly. A game that's fun to play for everyone, and just how involved you get into the missions, lore, events, PvP, etc, and how much time you invest into the game is entirely up to the individual player.
. ( you m8 consider going for advertising xD ) 
