Having said that, the argument put forward in this article is nowhere near complete. Yes, when you're getting paid by the hour the client has his foot on the gas pedal, but in reality he's already sunk a big hunk of money on you, from his standpoint on a long project it can easily look like throwing good money after bad.
Yes, agile techniques make clients happy faster. But it all depends on where the risk is. And there is a difference between the client and the users. If the users have a hard time making up their mind what they want? Then the software process becomes part of a business decision support system. The team interviews multiple stakeholders and facilitates negotiation and conflict resolution.
You might say "that's not software work," but that's the real world with real humans in it. In that case, it could be easy for the client to see bills every week or two for what he thinks is just a lot of talking, From his standpoint, he just wants the coding done -- and of course the users should be happy. (grin)
Because it is so complex hourly is the most straightforward way of working. I've been watching this scene for many years, though, and I have the sneaking suspicion that fixed price bids are what separate the men from the boys when it comes to delivering technology solutions -- mainly because the profitability can swing wildly from rolling-in-the-bucks to sucking-wind.