I've got one of the square ones on my desk at work, and I can't get used to looking through the magnifier. For me, the magnification benefit is cancelled out by the distortion. Moving my head moves the view and focus far too much to be useful, and my hands aren't where I see them, and, because I can see my wrists, my arms get confused. Maybe I'm just dumb, but it doesn't work for me - Some of my coworkers do all of their work under one of those.The light, however, is very nice - The color doesn't make my eyes tired, and I always have it on when soldering. Sometimes, I tolerate the distortion because placing the light between me and the soldering iron redirects the fumes out of my face.
Since you asked, the best magnifier is a stereo boom microscope, and they're priced accordingly (Think $1000-2000 for an industry-grade model). Think of the question "What is the best power supply." The answer is the $1500 Agilent, but a modded computer PSU will also work. That's the contrast between the stereo scope and the boom light.. We have models like this in the labs at my school and work; if you need the best, and can afford it, this is what you want. Maybe you're starting a business or something, I don't know. It's got to be stereo, because that's what gives you depth perception. A ring light around the lens is also a necessity; at high zoom, the ratio of the lens to your pupil diameter divided by the magnification means that a lot less light is going to your eyes. Something in the range of 8-40x zoom is good for soldering, you won't need more unless you're a magician with your soldering iron. Most of the time, 8 to 10x is adequate, and I just zoom in for inspection.
Scienscope carries more reasonably priced ones than the name-brand Luxo (Reasonable being $600+light source), and other stereo boom scopes run for around $500 on eBay. You can also get the traditional microscope style instead of of the boom, like the National Optical 400TL that you used to look at frog livers in high school for as cheap as $175 new, or look on eBay.