Tmiv and I got started playing FFXI yesterday and almost immediately ran into a new questing system that was added to the game. (Well, it was added in 2008 so 'new' is a bit of a misnomer. But I'd never heard of it before!) The basic idea is there's a big floating book located at the entrance to a zone and you can ask it for a quest. You get to pick from a list of quests for the zone which all seem to be kill n of mob X and maybe m of mob Y. Kill everything on the list and immediately get rewarded with a pretty substantial amount of bonus experience, gil (FFXI's main currency), and tabs (the Fields of Valor specific currency). Return to the book and you can pick up a new quest. However, only the first quest each day gives all the rewards. Subsequent quests just give the bonus experience.
As an aside, they also substantially buffed the experience earned for killing monsters slightly below you in level. That change coupled with these quests apparently let pretty much any job in the game solo reasonably well now. When I used to play at level 9 I was lucky to kill a monster worth 15 experience. Yesterday I was getting 150 from the same level differenced mob.
That all seems pretty straightforward but the question I had was what good were tabs. Is it worth making sure you come back every day to earn the tabs or should you just do the quests for the experience? Well, tabs do two things for you. You can spend trivial amounts of them to gain temporary buffs to help you solo. (They're the equivalent of white mage buff spells or eating food. So certainly useful but not game breaking.) Or you can save up a bunch of them to force special bosses to spawn. (FFXI seems to be really big on collecting trinkets to spawn bosses.) For an idea of scale here I was getting 30 tabs per quest and it would cost 15 to get protect cast on me. It costs 100-450 to summon a boss.
Before you spawn the boss you make a bet with the book that summons the boss. You can bet gil and if you win the fight you get twice as much back. You can bet beastman seals (items that mobs randomly drop which you can cash in to summon bosses) to get back 75 experience per seal if you win. Or you can bet a piece of gear and if you win you get the gear back with random stats added on to it. You can only bet unmodified items which are unbound. In all 3 cases there are restrictions as to what you can bet as well based on the level of the monster. (The easiest boss has a limit of 3 seals, 150gil, or a level 5 item.)
Fighting bosses is fun so I want to collect tabs just to fight more of them but the rewards seem pretty underwhelming. I guess buying extra copies of vendor gear to get bonus stats is nice when it comes to leveling other jobs but it doesn't seem like the sort of thing I need to obsess over maxing out.
There is also a restriction on how often you can summon one of these bosses. You can only summon one per earth day. (Resets at midnight in Japan or 11am my time.) You can bring a full party of 6 to the fight and each of the 6 people can summon their own boss. Also, I should clarify that the quests themselves can be done once per Vana'diel day which is 57 minutes and 36 seconds long. (25 game days per real day.)
My gut feeling is the bonus to experience and gil is nice and the quests provide focus in terms of what to kill so it seems reasonable to do but if you skip over it you're not missing much.