This is a very interesting question, and the responses seem to vary widely as well.
I've played a number of MMOs over the years, and have pretty much been a participant in the industry since it began. I think "loyalty" is an interesting concept as applied to MMOs, because players (being human) invest all manner of emotional capital into the game. As thinking monkeys, we demand of ourselves that our actions have value; if we don't perceive this value, we stop doing whatever it is. Having a sense of "making a difference" is critical to keeping people motivated, and in this context motivation constitutes sticking around and continuing to deposit.
From the developers' perspective, the customer base is an aggregate, and decisions have to be made from a business perspective - what makes sense here? Will we draw more members by doing X than will be alienated? Would we rather severely annoy a few high level, high value players by changing something to maintain game balance, or mildly annoy a large number of low-level players by leaving things alone? Each of these decisions gets confronted every day by the devs in any game... and they quickly realize that there is no "correct" answer, only trade-offs.
From the players perspective, this big picture approach is rarely (if ever) considered, since their experience of the game is so personal. Because of the investment of emotional capital, the actions of the devs are taken very personally... which we see every day on gaming forums. "How could you do this to ME?!??! OMFG I'm leaving/never coming back/killing myself/tt'ing my <blahblahblah>..." This trips up most gaming companies because they never expect it... to the dev, the decision to change the X to Y is an impersonal one, and they never expect the frothing rage it inspires in those affected by it. MindArk is no exception to this. It has taken them four years to begin to realize how their actions will be perceived by the community and to begin to take steps to communicate more effectively.
All that aside, am I "loyal"? Well, yes... this has been my game of choice for a number of years and a number of reasons. I value the player base - they are in general more mature and more responsible than the average MMO because they have an incentive to be. Once money is involved, people act MUCH more predictably than they do where they simply pay for access. This keeps griefing and general assholicism down to a dull roar (as opposed to, for example, Barrens chat from that other game). I also see a level of analytical rigor in the playerbase that I have rarely if ever seen anywhere else, as people try to make sense of the world around them. Plus I'm just fascinated with virtual economies
I've learned more about market-driven pricing from this game than I ever did from my textbooks.
What would cause me to leave? Probably not a different/better game. I am concerned about several trends I've seen emerging, including a) the rising cost of play for the average player, b) the emphasis on large, casino-style "jackpots" resulting in less loot for the other players, and c) the declining player base. MA seems to have a "tin ear" when it comes to marketing and PR; they do a very poor case of presenting themselves to the gaming community and explaining to potential new players what it is exactly that makes them "stand out" in the crowd. What little advertising there has been focused most on the people who were least likely to stick around... the "get rich quick" crowd, always looking for a shortcut to fabulous wealth. EU isn't that, and never will (or should) be.
Because of this complete lack of advertising, it's unknown even among hardcore gamers. MA's executive management has also made some highly publicized PR blunders, starting flamewars with influential figures in the virtual economy fields (*cough*TerraNova*cough*) which alienated the very people that we should be relying on to spread the word about what makes us better and different.
In my opinion, EU can compete _very_ favorably for marketshare with current players of other immersive MMOs like SL and EvE... the community in this game is involved at a comparable level, and that is a major selling point. We all care enough to dump tens of thousands of dollars a month (collectively) into this gaming company - that's an amazing thing. We have players that run events for other players, players who specialize in helping other avatars with their appearance and living quarters, players who offer all manner of services, including even players who will act as bodyguards, hunters, miners, etc. on commission! None of that is (afaik) possible in any other game on the market! But none of this ever gets mentioned... it's always "come hunt/see our booth babes/get rich!" The marketing campaign I would wage is "Come to Entropia, where YOU can make a difference!" LA owners solicit feedback on their areas, people trade amongst themselves, etc.... all of this is treated as suspect by MA, but they should encourage this sort of thing. Every ped they lose in "fees" is going to be richly rewarded by people's investments in the future once they have invested the emotional capital to make putting more real world money in the game seem like a good idea.
Oh well, let me get off my soapbox!