I have, however, seen my fair share of MMO blunders that ESO should try it's hardest to avoid, no matter how far into development it already is. In no particular order:
* Launch with the correct amount of servers.
Not too few, certainly, but don't make the same mistake SW:TOR did and have 120+ (North American alone) servers at/shortly after launch, and watch them nearly all become ghost towns when the initial player base lowers and evens out. This a huge issue for many TOR gamers, and has caused a lot of cancelled subs. Mild server queues are expected for a popular MMO launch. Increase server caps BEFORE you open new servers.
* Control how fast the population is able to reach Endgame.
(This is primarily concerning PvE endgame; not so much PvP)
This is particularly important at the launch of an MMO. If your game is easy-mode and allows effortless powergrinding, your gamerbase will find themselves with not enough to do when they reach level cap. Now, naturally, it's assumed that an MMO will have some form of Endgame at launch. No MMO I've ever seen though had what I would call an "abundance" of endgame material at it's launch though, and letting a massive chunk of your playerbase quickly level to the cap will cause ESO to stagnate for a lot of people, very early on. Again, this was a huge mistake of SW:TOR's.
Impose subtle speed bumps initially, so that people still enjoy the leveling process and are driven to reach endgame, but don't make it appear like you're overtly trying to slow down their progress. Use the time that people are racing to endgame to continue to develop and polish content. Be it an across-the-board EXP reduction from quests or a temporary increase in the amount of EXP required to level (these figures not being known to the public). Again, do this just at the beginning of the game's public launch. I highly doubt the game will launch with what a lot of WoW/TOR transplants will call a "complete endgame". Buy yourselves some extra time to continue to work on/polish the goodies after launch. I really feel I am understating the importance of this...
* Actively listen and interact with your playerbase.
ESPECIALLY DURING BETA TESTING STAGES!
I hate to keep using SW:TOR as an example, but as it's my most recent MMO...
The TOR team really did a terrible job when it came to community. Compare this to RIFT, whose Devs and CMs would actively interact with their playerbase. It doesn't even have to be a lot, just talk to them. Regularly. I realize as much as anyone how nightmarish an MMO forum can be, but svck it up and keep communication open. Note that I am not saying give in to even HALF the stuff your forum community is screaming about. Most MMO "vets" will tell you the simultaneously best and worst thing an MMO company can do is give in to the community. Most of an MMO's players don't even bother with the forums, anyway. Forumgoers are not the majority.
* Regular maintenance schedule and an effective patcher.
Pretty self explanatory. Depending on how many regions ESO will serve, try to pick a day and time that will inconvenience the fewest amount of players possible. Note: someone's always going to be put out. Fact of MMO life. Also, while a lot of your players accept that crashes and emergency maintenance will happen, do try your best to keep them to a minimum (not that it even needs to be said).
Also, nobody likes downloading 300mb worth of patches going at 8kb/s. Do whatever is necessary on your end to have a beefy patcher. The rest is up to the playerbase's ISP. Also, people will sing Zenimax's praises if you can pull off streaming patches to the game while playing like WoW has. And last, but definitely not least:
* Bugs, glitches, performance issues and server crashes.
For the love of Akatosh, don't have "one of those" MMO launches. I'm talking where your game hardly even qualifies as BETA. Three words: Final Fantasy XIV. That should say enough, and suffice it to say I'm still severely depressed at how they lauched it. Anyone play Mortal Online at launch? A majorly promising game... old school UO gameplay with an Oblivion interface? Yeah, the game looked and felt like it was coded by my grandmother. Also, honorable mentions go to SWG, WoW and Vanguard. Delay the game if needed. Certainly don't rush it. Make the best use of your beta testers' feedback as possible. Remember... you only get one launch!
I could go on and on with ideas, but I really just want this thread to be about LAUNCH ISSUES. With Matt Firor from (the best years of) DAoC being in charge, I have a good feeling about what he's going to do with ESO. Particularly with ESO having a 3 faction system as DAoC did. RvR awesome sauce, anyone? Both MMOs and players' expectations have changed since DAoC's glory days though.