I took the plunge and bought DxO Pro Elite. I'm now figuring out how to use it in my workflow.
One initial experiment was checking out what DxO does automatically and comparing with what I get without DxO. So far, the process I've used has been importing files from my EOS 5D in RAW form (CR2) without specifying presets and without intervening manually. I've then exported the file from LR to DxO, where again I've just let it get on with the processing automatically, without changing presets. DxO then pops the finished file back into LR.
I've posted some results
here - I make no claims of artistic/photographic merit but the comparisons may possibly be of use as an example of the results DxO gives to a guy who is by no means an expert user.
Net-net - I'm pleased I splashed out the money and looking forward to finding how best to use DxO in my workflow.