Summary :

1. Not worth the price ( 176%"4870 1GB" performance for 400 USD)

1.1 Current 4870 1GB Price---> 150 USD (USA)
----> £99~120 (GB)

1.2 Price cut

2. Performance wise ( Good, but not great )-->

2.1 20 SIMD VLIW Cores ( VLIW Compiler Quality)

Local Data Share + Global Data Share ( Not sufficient )

2.2 Good Backend capability for 4AA~8AA (Rop from 16-->32 )

2.3 RV870---> DX10 RV770 + 40nm Node+ DX11 Tessellation ?