Definitely a Top Tier Pokemon, yes outclassed by Rayquaza and eventually Garchomp, however definitely not a 'mon to pass on. Save the candy and wait for the eventual return of Rayquaza. Would be a good addition to a team that is going up against rayquaza with flying moveset!
And also (In my opinion) Palkia looks freakin' awesome! Adding some variety to your 6 unique dragon team!