The PhotoShop plug-in vesion version of DXO 4.0 is scheduled for release sometime soon. I'm hoping that fits into my workflow better than the standalone, and has a better interface too. I bought the 3.5 version last week, and though the interface is a little strange, I figured it out pretty quickly, and no longer mind it so much.
I've always used the PTlens plug-in for for lens correction, and it does a fantastic job for the money. DXO is a hair better (possibly because it computes its correction with the distance variable), but drastically more expensive. I use the Neat Image plug-in for noise control, and so far, I haven't gotten results from DXO that are anywhere near as good as Neat Image. Not even in the same league. PTlens and Neat Image also work with a far greater range of cameras and lenses than the limited selection in DXO. In both cases, you can tune those two plug-ins to pretty much whatever equipment you own, including scanned film images, which DXO will never support.
But some of the new capabilities promissed for DXO 4.0 could be really terrific, esp. the advanced geometry and perspective corrections. That's what really intrigued me enough to make the purchase. Guess we'll have to wait and see.