it isn't actually a 1.7.2 version, just 1.6.4. that allows 1.7.2 clients to connect, so you don't get new items & biomes etc.
You have to download the craftbukkit source, manually edit some properties and files so as it will accept 1.7.2 clients, and rebuild the .jar with maven. It technically isn't 1.7.2, it's just 1.6.4 with 1.7.2 clients, the only purpose for this is plugin usage. HOWEVER: Since the chances between 1.7.2 and 1.6.4 are so big and different, you can't just change the client version, and you have to change several hundreds, if not thousands pieces of code, and completely rewrite other parts of it. The servers you have seen probably have at least a few coders with an in depth knowledge of java and if you don't have either this or the time to do it, i wouldn't recommend trying it yourself, as you will probably kill your server.
There is no Bukkit for 1.7 as of now. It will come when its ready. Locked to prevent trolling in thread being a topic that was answered multiple times.