The creative minds of ASUS' engineers went all out when they designed the EAH4890 TOP. Higher clocks out of the box have almost become standard for non-reference designs today. What seperates ASUS from most other AIBs is that they changed the cooler and modified the PCB design quite a bit. While the black PCB is purely aestethic, the SuperML capacitor is not. On paper such Multilayer Polymer Capacitors look good and you can put a lot of technical talk about them on the box and in newsletters. In reality they are more of a marketing gimmick (we have seen much worse) than what they do for the performance of the card. Overclocking itself is a very fuzzy area - barely two cards overclock exactly the same. This makes is much harder to quantify any such gains. I do believe that the SuperML capacitor provides an improvement. Whether most typical overclockers will reap its benefit when working with this card, I don't know. Let's face it, the majority of graphics cards owners unpack the card, install the drivers and then game on. Still, kudos to ASUS for coming up with such a nice idea. A feature that definitely helps is the new dual fan cooler. It provides low temperatures and seems to be that critical element when it comes to voltage tweaking. It handles more heat (from voltage) better than the stock cooler which allows operation at higher voltage and frequency before being limited by the cooling solution.
I have a feeling that ASUS designed their card with much higher 3D default voltage in mind. It is perfectly safe to run 1.4V VGPU all day, even 1.5V shouldn't do much harm. The process of voltage tweaking is very easy thanks to ASUS' included Smartdoctor software, where voltage control is just the click on a slider away.
One major drawback of the EAH4890 TOP is the noisy fan. While I could justify the noise level under load with the goal for lower temperature that allow higher OCs, the idle noise simply does not make any sense. The card idles at cool 45°C, plenty of temperature headroom for quieter settings.
If you are willing to do some serious tweaking adjusting overclocks, voltages and fan settings, then this card seems to be a very viable choice for you, given that the price difference is not too much to a normal card. If you just want the best experience out of the box without spending a lot of time, I believe there are better options available right now. As hardcore overclocker you are still best off cherry picking from a large number of cards from multiple manufacturers. I have a feeling that the really good 1 GHz+ ASICs are going into some dark bin at AMD to be used on a future product that runs even higher frequencies.