(NOTE: While this isn't a wireless product, strictly speaking, it
performs much the same function, and can also be used to expand a
wireless network by connecting access points together.)

<http://www.reghardware.co.uk/2007/01/22/review_netgear_hdx101/>

It's a neat trick being able to transmit data around your home or
office via the mains power wiring. You get a more stable, less
interference-prone connection than Wi-Fi and a potentially faster
link too. The downside is that there's no roaming, at least not
beyond the reach of an RJ-45 cable and however many powerline
adaptors you've got dotted around your house.

Just as Wi-Fi is due to get a major speed bump, with 802.11n, so too
is powerline Ethernet. The difference: the 200Mbps powerline is here
now, while the 380Mbps 802.11n isn't going to be ratified until later
this year, though we're likely to start seeing a raft of standard...
almost products come in the next few months.

Scenting an opportunity, makers of powerline network products are
beginning to push the faster technology, particularly now that
consumers are starting to ponder streaming HD video around their
homes. With that in mind, Netgear last year began packaging its
already-available HDX101 200Mbps adaptor as a pair of units in a
'starter kit'.

Netgear was able to get to market well ahead of its rivals by
adopting a different technology. The best known powerline system, the
de facto standard, is HomePlug, touted by the HomePlug Alliance.
Almost everyone supports HomePlug's 14Mbps and 85Mbps standards.
Unfortunately, delays to the ratification process meant the 200Mbps
HomePlug AV specification wasn't approved until the summer of 2006.

In the meantime, chip maker DS2 had already started offering 200Mbps
powerline chipsets by adapting an existing European standard called
Opera, developed for broadband connections between homes and
electricity sub-stations. Alone among powerline Ethernet adaptor
vendors, Netgear chose to use the DS2 system rather than wait for
HomePlug AV to be finished.

If you already have 14Mbps or 85Mbps HomePlug-based powerline
adaptors in place, any HDX101s you add will happily co-exist with
them, Netgear claims. But don't expect them to communicate with each
other. Opera is incompatible with HomePlug 1.0 (14Mbps) and HomePlug
1.0 Turbo Mode (85Mbps). Nor is it compatible with HomePlug AV.
Which, in case you were wondering, isn't compatible with the slower
HomePlug specifications either but, again, will co-exist with them.

....

I used two HDX101 units to connect a MacBook Pro and a Sony Vaio
notebook between upstairs and downstairs rooms in my apartment.
Powerline Ethernet adaptor suppliers warn against using multi-socket
boards, but I had to and so, I suspect, will many other users. Avoid
boards with surge-protection circuitry - that's the killer, I'm told.
For testing, I used a simple two-socket extension cable with nothing
plugged into the second socket.

I first used the open source network testing tool iperf to measure
the link's TCP and UDP available bandwidths and got 56Mbps and
59.4Mbps, respectively. That compares to the 50.6Mbps and 59.4Mbps I
recorded for the Devolo units over the same stretch of mains cabling.
It's worth noting, perhaps, that when monitoring network usage with
Windows Task Manager, the Devolo box produced a smoother chart than
the Netgear.

....

Verdict

Netgear's HDX101 is a solid powerline adaptor, but there are a couple
of points to consider before buying one. I wouldn't hesitate to
recommend it for performance, but there's the little matter of its
incompatibility with other so-called 200Mbps products - if you want
more units, you'll have to buy HDX101s if you want them to talk to
each other. It's also quite a chunky unit, and it does suffer from a
much slower connection initiation speed than its rivals. On the plus
side they're about £20 cheaper than, say, Devolo's equivalent units.

Cost is a significant issue:
The kit of two HDX101 units is $196 from Newegg.com
<http://www.newegg.com/Product/Product.asp?Item=N82E16833122168>.

A better bet if you don't need the extra speed is probably the ZyXEL
PL-100 85Mbps Powerline Ethernet Adapter, normally $60 each from
Newegg.com, but currently only $40 each after mail-in rebate:
<http://www.newegg.com/Product/Product.asp?Item=N82E16833181019>
Review:
<http://www.reghardware.co.uk/2006/01/23/review_zyxel_pl-100/>

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>