I had a standard helmet for years, and then I borrowed a friend's cheap auto darkening helmet. (not sure on the brand) I'll admit that it was a great improvement, but I did notice that it did not get dark enough, and my eyes hurt after hours of welding.
I recently took a TIG class, and I got a Miller. Well worth every penny. This helmet should last me many years. And the difference is night and day between the two. I can actually see the weld puddle now, which makes my beads look ALOT better.
Just think of it as an investment that will last you many years, and a cheap insurance policy. You can't replace your eyes.
Just my 2 cents...
Michael