Like many other people, I am enjoying the story of the game so far. I am in no rush to make level 50 as I am enjoying the journey of getting there.
I do think that there needs to be some really good story driven end game content for people that do reach level 50. For me when I reach level 50, I am going to make another character and play that character to level 50. Right now I have a Jedi Warrior, next I am going to do a Sith.
I think that BioWare has done an excellent job at the game so far. The only gripe that I have right now and it is a minor gripe, is the lack of costume customization. This is only a gripe because in DC Universe we had a good deal of costume customization from the start. This for me is not really an issue though. In that game I reached level 30 and then lost interest because it really just fell short for me. The end game content was boring and in my mind was not worth the subscription fee.
That is what is going to keep this game alive, end game content, updates and expansion packs. On the other hand if you are playing 8 hours a day or more, then the game is not going to last that long.