A couple of times I have fired up my 10" netbook and used the Steam In-Home streaming with good results over WiFi. I did not look at the data transfer rate during the streaming process, but once in a while there will be a hick-up of some sorts.
With a wired network it will be better, but be warned... I did replace my switches a couple of times and my server is currently running on its 4th network card, and my HTPC on its 2nd. For some reason lighting fried the replaced components, even my network card in my gaming PC experienced some faulty connection issues.
For the above reason I have not yet connected my Xbox and PS3 on the wired network. Also I wanted to buy some of those micro ATX motherboard but they do not have space for a GPU and a extra network card. The same story with the Gigabyte Brix. If the wired connection get fried, you are stuck with a WiFi connection, and for some reason video files that are larger than +-5GB tends to get laggy on playback over my WiFi setup.
I have one PC running on those TP Link Ethernet power adapters and it is a lot better than the WiFi but it is slower than a normal wired connection (gigabit) and for some reason it fluctuates between 8MB/s and 16MB/s transfer speeds. This has been running for about 9 months now, and nothing fried yet