This isn't true, speaking as a happy retina MBP (15") owner. It's almost remarkable just how perfect everything, including fonts, look at the scaled resolutions. It certainly surprised me; the sheer tininess of the pixels really messes with your intuition with this. When you can no longer distinguish between pixels, things like scaling work far better than you have any right to expect.
The only time I have ever seen any issue with scaling was whilst moving a 1 pixel horizontal line across the screen on the "highest resolution" setting, and that's only because I was looking for it.
I have played around with a 15" rMBP in a store and colleague's 13" rMBP at work. Both exhibited the same symptoms in scaling modes other than 2x: font outlines were a lot more blurry than in the 2x mode.
I've owned the 15" rMBP since June. I use it exclusively in scaled 1920X1200 mode. Fonts are pristinely rendered to my eye. I'm very skeptical that you're able to detect blur in the font outlines at any reasonable distance in properly optimized applications.
What program were you using when you noticed the blur?
I must've gotten one of the few MBP Retinas that looks great at the non-2X resolutions. The non-2X resolutions might not be as sharp as the 2X resolution, but its still very sharp, and leagues sharper than non-Retina displays.
The only time I have ever seen any issue with scaling was whilst moving a 1 pixel horizontal line across the screen on the "highest resolution" setting, and that's only because I was looking for it.