I recently picked up a Lansky Turnbox and if you can believe it I was actually angry about how easy and effective it was. I always knew they were idiot-proof, but I never actually experienced it for myself. It took about 1-2 minutes to get an old Classic SD hair popping sharp, with my brain running on autopilot the whole time.
They cost 20-25 bucks. You've got two sets of preset angles like with the Sharpmaker, only you get 20 and 25 degrees with round sticks on the Turnbox whereas the Sharpmaker has 20 and 17 degrees I think? 15 degrees. If you own a Sharpmaker then it might be a good idea to supplement it with a Turnbox because they're so cheap, although a lot of people say they never use the 25 degree holes anyway.
I would get the Sharpmaker. I think it's worth the extra money over the Turnbox because you get the triangular shaped sticks which are more versatile at sharpening all kinds of different style blades.
A note about the Turnbox: they've got questionable quality control. If you get one, measure the angles. Mine were fine, but I've seen reviews complaining that the angles were off, and also some complaints about the sticks not fitting well. You won't risk running into that issue with the Sharpmaker. Although on the plus side, the wooden base of the Turnbox means you can drill your own holes at whatever angles you want if you are inclined to do so.