Shamefull disclaimer first.... I love DxO OpticsPro.
I really wish that DxO had DAM capabilities but, even though I really wish that it was up to the task, trying to do so is a preverbal "square peg in a round hole" situation. Because of that, I need to find a way to use OpticsPro (and ViewPoint) with my DAM of choice.
Because it's not a DAM, I typically don't use it for ALL of my images. Typically, I only use it for my selects. Things that I'm going to share online that would benefit from the superior (IMHO) RAW processing and noise reduction. That may change now that I can roundtrip via a simple plugin (I'm in the process of migrating to LightRoom), I may use it more than I did in the past. In Aperture the workflow was more difficult (Catapult made things a little easier but it still wasn't ideal) so it put me in a situation where I had to really feel that I'd benefit from going through the extra work of processing via DxO. Where I use DxO in bulk is when processing high ISO files, I find the de-noising in DxO to be well worth the price of admission. With Aperture this would lead to a bulk export/import and manual stacking, I'm still not 100% sure how I'm going to work through this with LightRoom.
DxO's integration with LightRoom is actually lightyears ahead of what you can do with Aperture (see what I did there?). I've done a few "round trips" and it works really well. At this time, I've only tried an image here and there so I'm hoping that it will work in much the same manner for bulk processing (like Catapult did with Aperture). For the few images that I have passed back and forth my standard practice is to return a TIFF back to LightRoom and stack it with the original RAW file. Personally I find a TIFF more transportable than DNG and, unless I'm uploading to the internet, a JPEG is never acceptable. The integrated DxO/LightRoom workflow is also nice in the sense that you retain your .DOP file right with your masters making quick DxO touchups a breeze, with Aperture those .DOP files were always a pain to retain/reuse.
The only real issue that this presents, of course, is storage (and time, I suppose). For every file that I send to/from DxO I effectively double my disk requirements. Quite honestly, this is an easy problem to solve, much easier with LightRoom than Aperture. That's why I have a NAS (filled w/4tb disks) for central/archival storage and a DAS for my primary library file (ThunderBay Mini filled w/1tb SSDs). In this scenario, the biggest issue is really the additional bandwidth required for my offsite backups, especially after shooting a basketball game at high ISO (which could be up to 1500 photos in a single night). Offsite backups just take more time, not much that I can do about that.
As I work with LightRoom I'm sure that I'll nail down a more specific workflow but, for now, it's a learning process. I would really like to hear how others are doing this as well. Great topic, maflynn...