Adding to Greiger's previous wall of text:
There are lots of little, unmarked secrets scattered around (i.e. lorebooks), so exploring isn't completely unrewarded.
The RvR area is reasonably big and castles reasonably spaced out. The landscape is mostly hilly, so there are plenty of potential routes between locations, and sneaking deep into enemy territory is very possible. Respawn points are placeable and destroyable like any siege structure, and castles have more than one entrance, so defenders should be sneaking out and ambushing the siege group rather than staying holed up in the castle waiting for the gates to fall. Some players in chat were comparing the RvR to Dark Age of Camelot's, though not having played that game myself I can't say how reasonable that comparison is.
The combat is fairly active. You can block any attack, and interrupt any special attack if your timing is good. There's no auto attack, and constantly running through your abilities will quickly drain your magicka and stamina. You can only slot five skills and one ultimate, so selecting skills that synergize well while distributing the load between your magicka and stamina pools is important. (You get a second skill bar at level 15, but I never made it that far so I can't say if swapping mid-combat works.)
You can buy multiple horses, and level them by spending gold at the stables. Horses have three stats: speed, stamina, and carrying capacity (which is applied directly to your character), so you can do a little practical customization there, with different horses for different purposes.
Crafting is ridiculously straight-forward. There's technically nothing preventing one character from mastering all crafts, though spending skill points on crafting skills means you have fewer skill points for combat skills. You'd also have trouble with inventory space if you try to do most of the six trades on a single character and aren't willing to put up with mules. (Mules are easy to use as the bank is account wide.)
Armor styles look decently reasonable, and there are a wide variety of them at all levels. There are two styles that can be skimpy (bosmer and argonian), but they are equally so for males and females.
There will be discounts for bulk subscriptions so you don't have to pay $15/month if you think you'll be playing for a while.
There's no way to graphically indicate targets, and players in a large group can look same-ish. There's also no way to target healing spells. This makes group PvP different, and communication more important. Small, organized groups may be more viable here than in Guild Wars 2, but I've only clocked about ten hours in TESO's RvR, and the zergs during beta were probably larger than what would be normal post-release.
There is the matter of the cash shop. So far, the only thing they've indicated they'll be selling there is the Imperial Edition upgrade, but that's arguably a reversal from their original position of only selling account services. They have said they'll be providing additional content to subscribers on a regular basis, but they haven't gone into any detail on what that content will be like.
Ignoring the TES lore, it's a fairly standard fantasy MMORPG. It tries to do some things differently, mostly in order to be more immersive, and some of it is problematic (the phasing), while some of it is stuff players will have to get used to (the lack of nameplates). The RvR is better than most recent games, but it's not for everyone. The main uncertainty here is Zenimax; this is their first MMO so there's no telling how they'll manage the game in the long run, and their business model and approach to beta has been somewhat strange.