Summary: I'll begin by saying my knowledge of computers and components is better than mediocre, but if you are looking at this model, you probably know as much as me if not more. That being said, this RAM is easily the best I've ever bought.
The CAS Latency timings on these modules are very low and compared to probably 99% of competitors as fast or (more likely) much faster. This is the second most important speed figure next to the frequency (MHz) of the RAM, and in some cases even more important.
The other nice thing is the look of them. Great bright red color on the heat sinks. No practical value there, but it doesn't hurt (especially if you can see the RAM through your case window). I don't have a case window on my most recent computer -- the novelty of it wears off quickly, especially if you (like on my last computer) have tons of fans that all light up when on.
The nice thing about this is also it's desire to be overclocked. I haven't begun clocking the modules yet, but it's rare that a manufacturer actually puts on it's packaging that the product is especially good for overclockers. Most people are hesitant to overclock their devices, and to that I have only this to say: I used to be one of you, but then I came to the realization that in a few years the RAM will practically be worthless -- you might as well get as much out of it as you can (this applies to CPUs as well). Obviously there are risks to overclocking, so proceed at your own risk. Also, it'll shorten the life of your CPU (possibly your RAM too), but again, in a few years, they will be worthless and you'll probably be upgrading well before they have been affected by the overclocking. That being said, the benefits outweight the risks if you know what you're doing . . . just make sure you know what you're doing.
The price I paid seemed fair as well: ~$158 (including sales tax & S&H; circa October 2005).
Finally this was recommended by Anandtech.com for their Mid-Range Buyer's Guide (Sept 2005; and possibly other places on their site). [A thing to note on this specific guide, I built the system they recommended, but found that the audio module that you can affix to the motherboard, wouldn't fit due to the case fan that was impeding the placment of the motherboard. A relatively easy fix, I cut a piece out of the fan housing to solve the problem, however . . . it's strange that Anandtech.com would recommend a configuration that didn't work as spec'd -- I'll leave it at that.]
One con is that the speed of this RAM is relatively low 400 MHz (A.K.A. PC3200 [400 MHz x 8 = PC3200]). There are modules out there that I've seen that are much faster (up to twice this speed), however I don't know if that is at the risk of losing CAS Latency timings and that this actually is faster than many modules running at higher speeds (MHz). In any case, 400MHz seems relatively slow.
The second con is that I couldn't find 1GB modules for the XBL series (at least when I looked); I wanted to put in 2x1GB instead of the 2x512MB. However, I am pretty sure that the reason is that you DO lose CAS Latency timings when getting higher capacity modules. Also, you don't want to run 4x512MB modules because of the whole 1T vs 2T command issue when running dual channel. In any case, I realized that 1GB of RAM probably would be enough for the gaming computer that I built, and 2GBs would've just been overkill and a waste of money, but if you really want to run a dozen applications at once. . . .
Anyway, so far I am very happy with my RAM. Hopefully I'll get the RAM and CPU clocked to their very breaking-point and have an even more kick-azz system for no more than I have already spent.