re: How necessary is dethatching?

If the clippings were that thick, especially with Bermuda, it means you waited too long between mows. Bermuda likes to be cut low, but that means it needs to be cut pretty frequently to keep it healthy. An added bonus of staying on top of your mowing is that the clippings won't choke out your healthy grass, and it'll decompose back into your soil, promoting healthy new growth.

As far as dethatching goes, that's an annual chore for me. I do it on the last "cold" weekend in February (I live in the Houston Area, it never gets really cold here), right before everything starts greening up. I have a small lawn, so I just use a large leaf rake and do it manually. Gets the blood flowing and the heart pumping, even though it's only 1500 sq ft or so.