Note: This is Not a rant of any kind. I made this topic to inform those not familiar with how SE works with their MMO's so that they could.. "prepare" better. Nothing I say here is certain to be the case in FFXIV, but what I am going to say has a good chance of coming true.
1. Community relations: SE is notorious for not communicating with their players as much as western developers do. That is the case in FFXI, and it will most likely be the case in FFXIV as well. The dev team will however listen to the complaints, but if they will do something about the issues presented or not is up to them. They will not tell us anything beforehand. If you can not cope with this fact, you should look for another MMO. Be noted, though, that this doesn't make an MMO "bad" by any means, since the dev team has been doing pretty good changes since around 2005 in FFXI even without satisfactory player/dev interactions. Btw, you could see a glimpse of what's to come from the Q&A session that was held in E3:
Q: Will combat be more action oriented or turn-based?
A: We cannot talk about the battle system at this time.
Expect to see more of that if you decide to try XIV! ;)
2. GM's & support: Normal GM's do not have much power in FFXI, and this may not change in XIV either. They can only help you with the simpliest of issues. When it comes to things like account security, SE has learned from the issues in FFXI and has, for example, a Security Token available for FFXIV right at start. This will improve your account's security tremendously. However when it comes to recovering your account or even items inside the game, SE can be very strict. It can be a long and difficult process to recover your account in FFXI, and while I am hopeful that SE will make things better in XIV, there is a chance that this may not change.
3. Updating the game: If something is broken in the game (job balance or event wise), the dev team seems to favor making new systems and abilities instead of changing the old. They will go back and change things if needed, but most of the time they create 'new' to fix the 'old' (time popped kings system is broken => the dev team created a whole new "instanced" event as a fix). They also like to buff jobs instead of nerf them. I don't think SE can get the job balance right without nerfing a few things in XIV first, but after that buffing weak jobs should go ahead of nerfing strong jobs. They also don't know what to do with pet jobs, and are in general too careful about buffing them.
SE also doesn't test their content in large scale before releasing it to the masses. They have their team testing things before the update, but for the most part all the players are the beta testers themselves. Expect some tweaking after every update.
4. Endgame: In FFXI gear progression is for the most part, horizontal. There are a lot of sidegrade equipment available. Endgame events do not get replaced every update. What this means, is that after few years there will be a Lot of content available in endgame, because they will not replace each other in any way. The drop rates will be lower than usually, but you can do many things at once which makes it a bearable process. However they might go the other way in the new MMO, but I myself do not see this happening. They may tier it like in WoW for example, though.
You may have heard the words "Ridill", or "Fafnir" when talking about FFXI or it's problems before. I won't go into much detail about these problems, but they arose because of the dev team's unability to predict the endgame's size in 2003-2004. Nobody can be sure yet, but I can guarantee that with much probability there will not be such issues in XIV endgame this time around. I'd say that it was mostly due to the dev team's lack of experience when it came to endgame that caused the problems that have for some part lasted to this day.
5. PvP & PvE: The dev team is very pro-PvE and while there is some PvP content in FFXI SE hasn't got much experience from creating it properly. They may create more PvP content to attract those kind of players to their game, but it is Not their strong point. Those looking for mainly PvP based game should probably check out some of the other new MMO's coming out soon such as Aion. If PvE is your preferred choice, I think XIV won't disappoint you if it's anything like XI is.
Okay that's it, I'll add more when necessary.. and one more time, I am not trying to say that SE, the dev team, FFXI nor FFXIV are bad. I love FFXI, I will most likely love FFXIV, but all of us have to learn to cope with these things. Maybe it won't be as big of a disappointment when you heard it here first? You might even like the game more :)