This year is special naturally because of LeBron James. The reason why is because it's so hard to win an NBA championship. Just look back over the last 30 years. Most teams have 1 thing in common... they almost all have a guy who is considered one of the best players of his era (Jordan, Kobe, Shaq, Bird, Magic, Duncan, Olajuwon). Sure you have a few "teams" without that one star player that sneak in & win once or twice a decade (Detroit, 2008 Boston). But for the most part all championship teams are led by an all-time great player.
Which brings us to this offseason. Most peopleconsider James to be the best player for the next 10 years, or in other words the next Kobe, Jordan, Magic, Bird.Signing James does not guarantee a championship, but that team will havethe keycomponent to bea top contender for the next 10 years. Miss out on this chance, and it will be much more difficult to build a championship team - and you have almost no chance at building the next dynasty.
Everything else you're hearing is just filler. Everyone knew Dirk & Pierce would stay with their current teams. Johnson will likely have no impact (in terms of championship) regardless of where he signs. That leaves Wade, Bosh, and Stoudemire who are interesting only for the fact that whoever signs LeBron is also expected to sign one of these guys. Signing LeBron plus one of these guys almost guarantees you'll be a championship caliber team for the next 5 years.