I bought it a couple of days ago. I got the original for 5$ on a steam weekend sale a long time ago, and it's the only time I've felt I've paid too little for a game, so buying warband at full retail prize helps my conscience some. It's quite worth it though. The game itself is improved over the original, but what made m&b great was all the mods and everything point towards even better mods for warband.
And for those who are asking: yes, Warband is standalone.
Also, there doesn't seem to be much in the way of tactics at the moment. It would be cool to see if a bunch of players in a formation would work well compared to everyone running around by themselves like everyone did in beta.
The Taleworlds forum is a bit under the weather due to post-release strain so I can't post links, but there are a couple of multiplayer mods I think you'll like:
One is the Invasion Mod, otherwise known as "The Battle for Calradia". It pits players on one team against endless waves of.. interesting bots on the other. Sort of like a medieval zombie acopalypse, except without the zombies (although the bots are about as intelligent). Experience shows that the only way to survive any length of time is to form a proper shield/spearwall with archer auxiliaries and maybe a light cav or two to get the stragglers.
The other is the "Mount and Musket - Battalion" mod. It models a number of reasonably historically accurate nations from the time around 1800. It's perfect for line battles napoleon style. Great fun if organized properly.
A third mod is called "Hunt", which is 18th century hunters vs werevolves. Both sides need some internal cooperation and planning to succeed.
Note that I don't think any of these have been ported to the latest release version yet, but they're actively working it (the various modders all paused a couple of weeks ago in anticipation of the release since patches were a bit too frequent for a while).