Seems W9OY is causing some heads to broil on the Elecraft list, thanks to Julian G4ILO stirring the pot. ;-)
I don't know W9OY but I read his blog often because I'm fascinated with the whole SDR aspect of the hobby. He's as much a fanboy for the Flex 5000 as many are for the K3 (including me, I suppose). I have no problem with that, we all like to talk up the equipment we own. W9OY certainly knows his stuff, and even though he may toss out a jab at the K3 every now and then I just take it with a grain of salt -- no burning desire to break out the dueling pistols, it's just a hobby.
Often, though, I've heard hams on the air trashing the K3 as though anyone who owns one isn't just wrong, but stoopid as well. I call it K3 Derangement Syndrome: any mention of the K3 causes them to prattle on about how inferior it is to their radio. They'll harp about the K3's "poor ergonomics," as if pressing a button twice to move from 40m to 20m is somehow more of an inconvenience than having to boot Windoze every time you want to use your radio. They'll talk about the size of the radio, as if the compact box isn't one of the K3's attractions for many owners. They'll nitpick over specs, as if they really make a difference while working the DX. Mostly, it becomes evident after listening for a while that most of these K3DS sufferers have never actually used a K3, but merely heard all these horrible things from someone else. I guess the P3 will give them more ammo because it's smaller than Power-SDR running on a 60" plasma display -- your sophomoric "mine's bigger" kind of argument. Whatever.
Life is too short. We all have reasons for choosing the radios we choose. My big reason for not buying a Flex product is that it relies on Windoze; if it supported OS X, I might have one on my desk right now. But I have enough Windoze headaches in my daily life and don't really want them to be at the core of my radio hobby. As Bones might tell Kirk, "Damn it, Jim! I'm a ham, not a systems administrator!" Those who might actually enjoy dicking around with computers will almost certainly report different mileage. Good for them.
Another good question has already been raised by someone else: What happens in 20 years? I have a garage full of 10-year old computer peripherals that simply won't work with my current PCs and Macs. The Flex rigs, when you boil it all down, are computer peripherals. That it doesn't rely on USB drivers makes it more likely to be supported years down the road, but what happens if FireWire goes the way of 5.25" floppies? Or if future versions of Power-SDR no longer support anything older than the Flex 8000? To me, one of the things I love about ham radio is that people running vintage gear from the 50's and 60's are still able to do pretty much everything a guy with a K3 can do; with proper care and feeding, they can last a lifetime or more. On the other hand, computers and peripherals are throw-away items. Which category a PC-based SDR falls into, only time will tell.
That doesn't mean I won't someday own a Flex 5000 (or 6000 or 9000); maybe I will. Flex Radio Systems is every bit a great company as Elecraft, and their user base every bit as loyal. If I had the cash I'd probably own one now because I love the SDR concept. If someday it no longer works under Windoze 2036 or whatever cruel hoax Microsloth perpetrates on the masses in the future, oh well... out to the pile in the garage it'll go, to be replaced by the newest model. But I won't get rid of the K3 unless and until something else comes out that offers a significant improvement, and whatever may replace my K3 someday will sure as hell have knobs and buttons and be able to operate as a stand-alone instrument without a PC umbilical. These are my requirements; if yours are different, buy what you want.
And while others may take cheap shots at competing radios just to make themselves feel smart or superior to those who choose differently, I won't do that.
(I will, however, continue to take cheap shots at Microsloth Windoze. It just plain sucks.)