Ummm you can buy loot with them but that costs alot. You can buy a couple followers with them? But mostly I just use them for seals. And i heard once that you can buy some item from them and sell it for a profit (low profit) but i forget what the item was.
There is also a few mounts and pets you can buy for them if you are in to that.
Edit: I see now that the links don't link directly to mounts/pets. If you write mount or companion in the search box on the site you will get only mounts/pets.
Since I quit the apexis dailies when the retards dismantled them from raiding groups, I'm just saving them for the day I'll be able to get rep in a non-cheapasianmmogrindy way and buy the mounts and stuff.
Yes, I have a lot to bitch about.
Science flies you to the moon. Religion flies you into buildings.
To resist the influence of others, knowledge of oneself is most important.
The missions themselves are not rewarding it is their aftermath which makes them worthwhile, since each apexis daily gives you a nice chunk of boost towards a certain invasion, thus doing them occasionally can lead to a garrison invasion which can reward you with mounts and achievments.
That being said I think the only two worth doing is the Shadowmoon Enclave and the Everbloom Wilds one since they can be done in literally 5 minutes if done right.