I use both LR4 and DOP8. I have a long history with DOP and about 6 months with LR. A few points:Both are useful but have different strengths. LR of course offers local adjustments, and a fair ingestion engine. DxO offers notably more accurate distortion correction and and an easier/faster work-flow for images that are in good shape straight out of the camera.
DOP8 is a significant upgrade to DOP7 but in ways that DxO isn't likely to admit. It's the most stable version of DOP since version 5. Version 7 would fall over in all sorts of ways. DOP8 has been rock solid for me.
Secondly I strongly suspect that most of the code is new, which bodes well for future versions. Importantly the sometimes odd colour handling, especially with more extreme settings, is a thing of the past. The new DxO lighting control is easier to use than in previous version and yields more natural looking results.
DOP8 is well worth having along with LR4, especially for architecture and Urbex.