There are a number of different points to consider in a product like the SuperWorkstation 5046A-XB.
First, and perhaps most important given today's economic climate: cost. We're currently seeing the barebones platform selling for between $750 and $800 online. Were you to build your own "workstation" using an MSI Eclipse SLI motherboard, a Cooler Master UCP 900 W power supply, and a Cooler Master Cosmos S chassis, in comparison, you'd spend about $830 and miss out on Supermicro's integrated backplane—a true boon for adding and removing storage. While there are certainly a number of ways to pound that do-it-yourself price lower (you could easily go for less motherboard, less power supply, and less chassis), we're still fairly comfortable with the price Supermicro is asking for the purpose-built platform.
Next up is functionality. What do you get or give up by buying a workstation barebones? Clearly, Supermicro picks parts from its server lineup for this one. The power supply supports dual-processor configurations, but it seemingly wasn't meant for high-end PCIe 2.0 graphics cards. And while the chassis offers eight 3.5" drive bays, Intel's ICH10R only supports six SATA pathways—one of which gets used up by an optical drive. Fully utilizing the enclosure's capabilities means adding a PCIe x4/x8 storage controller, which might be a good idea anyway if you're contemplating software-driven RAID 5. Moreover, there isn't any overclocking flexibility to speak of in Supermicro's BIOS, so you won't be able to extract the available headroom from an affordable i7 920, for example.
On the flip side, just because the 5046A-XB's comprising components weren't tailor-made for each other doesn't necessarily detract from the platform's allure. We remain convinced that anyone going this route is going to buy either one AMD FirePro card or one/two Quadro FX boards. And unless your're planning on using a pair of Quadro FX 5800s, you shouldn't run into any trouble with Supermicro's choice of power supply or its connectors. It's also nice to have the option of installing as many as eight drives, should your storage needs extend out beyond what Intel's chipset can handle. And while it'd be nice to have at least limited overclocking flexibility, aftermarket tuning would just add unnecessary risk to a configuration originally engineered for reliability above all else.
Supermicro's 5046A-XB delivers on the company's promise of high-performance, quiet computing. It does so at a fair price using components that we're sure resellers would be more comfortable selling to their business customers than a lot of the mainstream desktop hardware we normally look at. To that end, it's important to remember that this workstation barebones is aimed at an audience anxious to get its hands on the powerful Core i7 architecture, but still likely to grab hardware RAID controllers and professional graphics cards, too. That it'll support upcoming Nehalem-based Xeons and ECC memory is a plus.
If, on the other hand, you're eying the 5046A-XB for its super-quiet chassis and efficient power supply (yet still planning to drop in a couple of Radeon HD 4870s or GeForce GTX 285s), there are probably less-expensive hardware combos that suit your purposes more precisely.
Check prices for Supermicro's 5046A-XB