Well I figured I'd throw up some comparison benchmarks and make a semi-review. Benchmarks ran under Windows 7 RC x64 with Catalyst 9.6.
Up first, the HD4850:
3DMark Vantage: Performance Preset
3DMark Vantage: High Preset
3DMark06
Far Cry 2
Crysis : 64bit Vista Compatibility Mode

Crysis : 32bit

As you can see, my HD4850 is clocked pretty high at 725/1225 (reference is 625/993), so the results are going to be a bit more competitive...
Now for the HD4890 benchmarks. These are done at stock clocks (870/1050).
3DMark Vantage: Performance Preset
3DMark Vantage: High Preset
3DMark06
Far Cry 2
Crysis : 64bit Vista Compatibility Mode
Crysis : 32bit
Overview of benchmarks - HD4850 vs HD4890: 3DMark Vantage
Performance Preset: 9137 vs 11027
High Preset: 5686 vs 7060
3DMark06
15986 vs 17872
Crysis
64bit Vista Compatibility Mode:
Minimum FPS: 13.54 vs 17.83
Maximum FPS: 27.75 vs 34.29
Average FPS: 21.13 vs 26.29
32bit:
Minimum FPS: 15.29 vs 20.02
Maximum FPS: 27.13 vs 35.08
Average FPS: 21.50 vs 26.95
Far Cry 2
Minimum FPS: 41.62 vs 47.08
Maximum FPS: 71.74 vs 87.22
Average FPS: 52.86 vs 63.13
Comments on Sapphire Vapor-X HD4890 Price: $265 @ DirectCanada Connections: It has everything you'd ever need. VGA, DVI, DisplayPort and HDMI. No need for bulky adapters here. Though should you need another DVI port, an adapter cable is provided. Also due to the placement of the VGA and DVI connectors, they are easily accessible even with my external 220 radiator that hangs from the rear 120mm case fan. With typical cards, it was a bit tricky to get the 2nd monitor plugged in and it was impossible to use anything but DVI on one of the ports.
Accessories: 2 of the typical PCIe to molex power adapters, HDMI to DVI adapter, driver disc, installation guide, case badge and a Crossfire connector.
Temperatures:
Idle: 57C @ 39% fan
Load: 77-78C @ 60% fan
Noise: Inaudible up to 60% fan speed over other case fans. Anything over that quickly becomes audible though even at 100%, it's not unbearable, but not something I'd want to here non-stop.
Overclocking:
So far, I've been able to do 970/1200 in Left 4 Dead (did a speed run of Dead Air) without issues, however firing up 3DMark06, it locked up on the 2nd test. I've yet to sort things out though my guess would be 960/1200 should be totally stable. Once I find the maximum stable OC, I'll post another set of benchmarks (probably without pictures) to show the effect it has. Sadly since it doesn't have a supported I2C chip, I cannot adjust voltages via software.