I've been using the cover with a light for a few weeks. It does its job, I can read with it. The two brightness settings are virtually the same, when I switch it on I don't care if it's at its highest or lowest, I barely notice the difference. I don't like having to keep the light from shining directly on the screen (causing a reflection in my eyes), but I'm glad I didn't go for the silver coloured reader as I expect the situation would have been more difficult to avoid. The added width has led me to buy a non-lighted Proporta cover (cheapest on Amazon.co.uk but not advertised as Proporta, check the images and reference number) too, allowing me to carry the reader in my jacket pocket when I won't be needing the light.
As with most of these covers, the clips seem fragile but have not broken. They are a bit flexible.
Anyway, the bottom line is that the inbuilt light does work, it isn't perfect, it is seriously overpriced, but it satisfies my needs.