I fail to see how this changes anything, other than you now have an additional network behind your router. The border gateway into your house from your ISP is already potentially "compromised" by them, in that they have the final say of how your public IP gets used. Setting the ISP's router into bridged mode and giving your own router full control of your public IP is really what you want. I'm finding, however, that this seems to be a dying trend (Time Warner's Roadrunner service still allows it, but they're hiding the page to set your router into bridged mode such that you have to know the direct URL to the router's page to control this...I imagine they'll probably just do away with this feature entirely in the future). As far as I know, services like AT&T's U-verse and Google Fiber don't even allow setting your router into bridged mode at all (somebody please correct me if I'm wrong).