Must admit that I have no interest in Aion at all, seems far too "easternised" for my liking. I know its toned down a little to be more appealing to the western market, but its still got far too much of the eastern thing going on about it for me.
I very much doubt it "WILL" be "THE" alternative to WoW whatsoever. To be honest, if I had a quid for every time I have seen someone spout that line prior (thats the important word) to an MMO release, I would probably have enough money to make my own MMO by now
I think it will do ok, will do infinitely better in the eastern market than the western market, but I can see it doing around as well as LOTRO or Guild Wars in the western market. In summary, I think it WILL be AN alternative to WoW (much like any other mmo), but not THE.
To answer the OP though, I had high hopes for WAR after the truly awesome times I had in Daoc, and to be honest I really did enjoy the beta for WAR. Strangely, and somewhat disappointingly, I actually found that the beta ended up being considerably better than when it went live. I'm still not entirely sure why that is, it could just be that playstyles changed so much once the game went live. Certainly the attitudes of the players altered a helluva lot once the game came out, simply wasnt the same after that.
Depends really upon what you are looking for in an MMO. I've tried for almost a decade to find one which is anywhere near as good as UO was (pre-trammel). Unfortunately I have failed to find that in any MMO since UO. Indeed since leaving Daoc many years ago, my attempts to find an even halfway decent PvP MMO have come to nothing, tried just about every major MMO around and none have grabbed me in quite the heartpounding way that Daoc and early UO did.
I'm enjoying LOTRO at the moment for its PvE aspect and much more importantly for its mature community (just about had my fill these days of mentally 12 year olds swearing left right and centre to act macho and spamming crap about chuck norris every 3 minutes in MMOs). PvP wise though, I think that ship has long since sailed. To be honest, the ship containing MMOs is not far behind it, especially as nothing seems to even be 10% of what UO was 12 years ago.