A lot depends on your prescription; glasses could be correcting lots of different issues. I'm around -5 diopters nearsighted. In real-world terms, without glasses, about a foot away is good. So going without glasses doesn't work for me*.
I used a magnifying eyepiece from Nikon, this one:
Amazon.com: Nikon DK-21M Magnifying Eyepiece for Nikon D200 Digital Camera: Camera & Photo
It's slightly less magnification than the Pentax, slightly cheaper, fits but not that smooth, but otherwise quite similar. It projects a bit when mounted, which might affect how the camera fits in a bag. I had to "look around" to check the status line and corners. On the *ist DS, that was fine. On the K-7, I thought it wouldn't work well due to the 100% coverage, so I left it off. I don't feel like I'm missing anything.
*Wife: "Can you tell what color that stoplight is from here, without glasses?"
Me: "Without glasses, I can't even tell there's a stoplight."