Bringing characters back from the dead on a constant basis is certainly something I agree should not become a standard in the movie universe.
This said:
1) Cyclops' supposed demise seems to have been deliberately left hazy and open for a return. His sin might have bubbled and Jean believed she killed him but the fact is you don't really know what happened, they never showed him disintegrate or give a reason why Jean was found the way she was. Both Marsden and Ratner responded in interview to his death by saying no one really ever dies in the X-Men universe and I'm sure that if anything the unexpected reaction his "death" had by fans will hopefully make the movie makers think of re-using the character and have a better role.
2) The movie pretty much countered every single stupid thing it did. From killing Xavier to having his ridiculous body snatcher ending (That is something I really wish they hadn't done) to have an indication that all the "cured" mutants will just get their powers back anyway as shown by Magneto's chess move.
3) This is only my personal opinion. As much as I hate the die and resurrect maneuver, frankly I do not feel the X-Men movies can work at all withou the original cast. Without Stewart, Jackman, McKellan, Marsden, Janssen and Berry the movies would not work. None of the younger X-Men can carry a movie on their own; neither with their characters nor with their talent. I love Paquin, Ashmore, Foster, Stanford and Page; what little they have offered was great, but they can't hold a movie together; even with support from Grammer, Cudmore and Cumming.
Without Jean, Scott, Logan, Xavier and Ororo, there is no X-Men movie.
My two cents.