The performance of powerline networking equipment is always highly variable; as an example, one CNET editor (who shall remain nameless) isn't a big fan of powerline networking as he consistently fails to get more than a couple of Mb/sec out of any powerline equipment. Other editors do much better, so take our figures with a large grain of salt, and keep hold of your sales dockets. We tested two DHP-300s in a simple network configuration to give the units the best possible fighting chance of hitting the near-mythical 200Mbps target, and commenced file transfers to get some real-world transfer examples.
We'd grown used to being disappointed by the hype surrounding 200Mbps powerline, and sadly, the DHP-300 wasn't the unit to dissuade us from this view; across a battery of tests with a variety of file transfers, the top speed we managed was a paltry 19.7Mbps, which isn't enough for solid HD video streaming. It's still relatively fast for home networking -- for reference, the same tests using 802.11g networking across the same machines got us no faster than 6Mbps -- but well below what's commonly claimed for this kind of equipment. Critically, it also performed much slower than Netcomm's less visually attractive purple 200Mbps AV Homeplugs. D-Link's offering is marginally cheaper, but it's also around half the speed in our test environment.
It's also worth noting that like Netcomm's and Netgear's offerings, the DHP-300 forms its own network and doesn't play well with others. In our tests, we were unable to get any of the three to see any other competing adaptor on a simple powerboard, although they'd all happily see their "own" make quite easily. Simply put, if you invest in any of them, your investment is stuck within the one brand.
Ultimately, the D-Link DHP-300 scores well with us for bringing the price of Powerline HD equipment down, but it's a pity that, at least in our test environment, it's brought the speeds down as well.