Even I am facing the problem.
Dell provides ATI driver ver 18.104.22.168 for my Notebook. The OS works fine with it. However, the graphics performance of the ATI 8670M card is poor with this driver. I removed graphic drivers with amdcleanuputility I have downloaded/installed and tested the version 14.4 of the driver from AMD web site and it provides a lot better graphics performance with the same card.
However, on clicking "Shut Down" the laptop doesn't exactly shut down. The LEDs are still on and the screen goes blank and the notebook becomes hot. It doesn't even wake up. The same happens when the system is in sleep mode. Doesn't wake up. The only way to shut down is long pressing the power button.
I confirmed the performance by various benchmarks. I have installed all the other latest drivers for Win 8.1 64 bit from dell support including bios, Intel HD Graphics and Video_AMD_W8.14_X01_A00_Setup-6GGGM_ZPE. I even talked to dell support but of no avail. I asked them to escalate the issue and get it resolved in consultation with AMD.
Now I have tried to contact the AMD tech support. Not sure if there will be an outcome. This is frustating. I'm eagerly waiting for a resolution.
Dell Inspiron 15R 5537
Core i5-4200U 2.30 GHz|6 GB RAM|Radeon HD8670M 2GB|Win 8.1 SL 64 Bit