I believe the OP was discussing the mulching of leaves in the fall on his lawn. Some of the responses are discussing mulching of the grass clippins when mowing. Two different things.
I've always mulched my autumn leaves right into the yard. I rake them out and spread them out over the yard and just mow 'em. I think it's the very best thing you can do for grass.
Always mulch them leaves if you can. I have a lawn service come and spray and in the fall they put down a granular then come back and plug it about the time I'm mulching the leaves. I'm usually always the first to mow in the spring.
When I had the time to do the job properly, I mulched the leaves and the lawn seemed to appreciate it.
The downside was that I needed to stay on top of things otherwise the leaves would overwhelm the mower - so this meant that I would be out there with the machine every other day or every three days during the peak time of the falling leaves.
I mulched my fall leaves with my Toro Recycler. Looked a lot better after the second mowing when the leaf pieces really got spread out, you can't see any leaves now. There is a narrow area along a retaining wall that I bagged and dumped in a wooded part of the yard when the leaves were heavy.