OK, it's not inexpensive but it really WORKS. My lawn has, over the years, been reclaimed from a field and, despite lots of attempts with various other products, the grass quality was always indifferent and patchy. Weeds were also a problem.
I used Scotts Lawn Builder last year and again a few weeks ago (spread very evenly by a Scotts EvenGreen Drop Spreader
- see my review) and the results are genuinely impressive. The weed population is now almost nil and the grass quality is both excellent and even.
I also always use the mulching facility on my lawnmower. It means there's no cuttings to clear up whilst the shredded clippings left behind by the mower function as a lawn fertilizer, as if I was applying compost to the lawn.
That, plus Scott's Lawn Builder - and not cutting the grass too short - is an excellent technique.