Modest light fixture - 15 watt, 18". I have no meter, this is just my own perception. I can tell you that I can look directly at the tube when on, and it is not annoying. Before, it was too bright to tolerate. Areas of the tank once well lit are barely lit now.
The initial burn-in only takes a few hours, not months. Some bulbs degrade faster than others. Just buy a new bulb, see how it looks like, and after a few days of burn-in switch to your old one and compare the two.
It was the tube, not the ballast. Significantly brighter, and this one is 6700K. Big difference in what everything looks like. Plants are considerably more green in appearance. Will be interesting to see if plant growth improves noticeably.