Back in the day, core rolebooks used to come in triplicate. You had your Player's Handbook, your DM's Guide and your Monster Manual (or some version of a monster book, be it a compendium or a manual or a folio). This formula was present at the very beginning when the first version of Dungeons and Dragons came in a boxed set with three books presenting character options, monsters and treasures, and DMing advice on running adventures in the wilderness and underworld.
Fourth edition has turned that notion upon its head, as each and every book that comes out is considered to be part of the "core" rules. The first Player's Handbook (because there are already two and there will probably be more) only presented a handful of classes with the understanding that more would follow - and follow they have. Each power source (every class in 4e draws upon a power source, martial power for a fighter, for instance) gets its own book with new options for existing classes that use that power source and new classes to boot. Individual races get their own book. Heck, Martial Power 2 is about to come out so even one extra book per power source is not enough!
In many circles, this ever-expanding core is a major strike against 4th edition. What happened to the days of just needing a player's handbook, DM's guide, pencil, paper, dice and imagination? Do they really expect people to shell out hundreds of dollars just to be able to make a character that can keep up with the Joneses?
The short answer to this is no. The idea that you have to buy all these books to utilize their content is rooted in an older age, an age that 4e is desperately trying to break away from. I recently bought a one month subscription to D&D Insider for $10, and that gets me ALL the content published for 4e to date, including stuff from Dragon magazine, all bundled into a nifty character builder that lets me easily search through all the options available for my Dragonborn Ranger (or whatever other character I wanted to make). One subscription also comes with five updates a month to the character builder, so basically your entire gaming group (or at least five of them) could have an up to date character builder for $2 each! This is not a lot of money. I plan on waiting a few months and then getting another month subscription to update everything, doing this either twice or three times a year for a total expenditure of $20 - $30 annually, which is about the price of a single core rulebook!
The D&D Insider subscription also comes with access to the compendium, every rule in the game fully explained with up to date erata included, and every issue of Dragon and Dungeon magazine. Now, I for one like the tactile sensation of holding an honest to goodness book, and I made my character and leveled her up for five levels using my physical copies of the Player's Handbook, PHB2 and Martial Power. Having gone through that experience and comparing it with making a character using the character builder, I can say that I vastly prefer using the character builder.
One of the most common complaints against later editions of D&D, and conversely one of the things held up as a major strength of earlier editions, is how long it takes to make a character. The argument goes that if you have to spend hours making a character (which was certainly the case in 3e) and you have to have a degree of rules mastery and knowledge of how feat choices interact with each other later down the road (which was doubly the case in 3e), this leads to an unwillingness to kill off characters because it just takes too long to make a new one. If you die in OD&D, B/X D&D or AD&D, heck, you roll up a new character and get back in the saddle within a few minutes!
Let me tell you, if you haven't experienced the 4e Character Builder first hand, it makes generating a character almost that quick and easy. Well, quicker and easier, actually, if you use the quick build option that lets the character builder choose your feats, skills and powers. But even if you hand pick each option, having it guide you through each step and present you with all the choices and their definitions without having to flip a single page dramatically speeds up the character creation process.
I think in many ways, 4e is much closer to the old school ethos than some people would give it credit for. It is certainly much more "old school" than 3e, with its dramatic reduction of skills and general de-emphasis on the penalty for trying a skill untrained and its rapid character generation.