Buying software is not like buying a vase or a comb or a lawnmower where you pay, you take it home, and the transaction is complete. No, buying software is more like joining a club with annual dues. Every year, there’s a new version, and if you don’t upgrade, you feel like a behind-the-curve loser.There’s a time bomb ticking in that business model, however. To keep you upgrading, the software company has to pile on more features each time. Sooner or later, you wind up with a huge, sloshing, incoherent mess of a program; a pile of spaghetti code that doesn’t run well and makes nobody happy.You’re in even worse shape if that bloatware is your operating system — the software you run all day. Just ask anyone with Windows Vista.This year, though, Apple and Microsoft both realized that the pile-on-features model is unsustainable.