DPF with DEF is far better than a DPF without DEF. It reduces the need for a much EGR, and EGR's are the big issue not the DPF.
I am a Cummins fan, but they waited way too long to go with a DEF emissions setup. The 07.5-12's are reliable, but get lower mileage and are more prone to EGR related issues.
They are probably all gone now, but I wouldnt be non-DEF shopping for a new pickup.