This waterblock has great potential for overclocking with any HD2900XT card. The temperature drops are fantastic and im certain that the watercooling of the PCB components helps a great deal in terms of stability while overclocking. There is not really any comparison between the stock OEM cooler and the DD-29XT waterblock. The maximum overclock I was able to achieve on stock voltage using the OEM cooler was around 850MHz core frequency and 2200MHz RAM frequency. Above this and instability crept in and I saw severe artifacting, system lockups and restarts. For instance, on the stock cooler, once I changed the core speed approaching 900 MHz on stock voltages and tried to play a game I got either a BSOD or insta-restart. However, I have been able to run Jade Empire @ 900 MHz core and 2300 memory for 30 minutes without graphical glitches, and this is purely down to the temperatures, as voltages remain at stock. This can only hint at what this card can achieve on increased voltage while cooled by this waterblock!
However, there are a few things which must be considered before using this waterblock. Even though the DD-29XT waterblock has an awsome cooling ability, alot also depends upon the rest of the cooling loop. If other components are being cooled within the same loop, such as a CPU and Northbridge/Southbridge, these may decrease the cooling capacity of the DD-29XT waterblock. The performance is also dependant on what type of radiator, fans, coolant and pump you have. If any of these are insufficient then the cooling ability of this waterblock will be reduced. Equipping a sufficiently effective watercooling loop for this waterblock may also be expensive, but if you want rock solid performance and graphics card longevity it is well worth the investment.
Overall the I would give this card a 9.5 out of 10 simply because it does what it states to do, and surpasses the stock cooling by enormous amounts. It is finely engineered and delivers the solid cooling performance we would expect from Danger Den. Therefore I can highly recommended the DD-29XT to anyone willing to watercool their Radeon HD 2900 XT graphics card.