Someone else had posted comments about the speeds over these lines so I figured I'd offer my experiences.

For doing large file transfers, yes they are a little slow. However, in terms of just about anything else they're completely sufficient.

In my house we regularly have up to three clients playing movies off the file server without issue. (In addition to standard internet browsing and occasionally running bittorrent off a laptop..)

I've got four of the DLink DHP-301 units running in my house and they're just terrific.

They're great for anyone unwilling (or unable) to tear up their walls to run CAT5. In my case, I'd have to go through three floors and I'm not exactly a do-it-yourselfer. These units were affordable enough (compared to losing a weekend and having to get help from a friend to run CAT5), and just plain work. I took a risk being an early adopter and I'd do it again if I had the choice.

I use them to connect my broadband connection and servers (in the basement), the media center switch (main floor), wireless AP(upstairs) and a second media center (upstairs).

Some of the advantages of these sort of units :
- Zero setup. Unless you want encryption on the line (and they're rare enough that's probably safe without), you just plug them into your outlets and you've got an instant network bridge
- Flexible. I've moved the placement of where I had my bridges plugged in a few times. With wired CAT5 through the house, I'd have to run Ethernet from wherever the drop is to wherever the computer or network printer happens to be.
- Mostly problem free. I've had these for about two years now and the only problem I ever have is having to unplug a unit about once every six months. I can live with that easily. :)

If you're wireless is being difficult and you're unable or unwilling to run cable, think about using Homeplug bridges.

Homeplug is basically ethernet over the power lines in your house. They usually sell the adapters in pairs which act as a bridge. So you could have one adapter in the office with the modem and your access point, and another in your living room going to a switch for your xbox/ps3/wii/laptop. So it basically turns any electrical outlet into a potential bridge point..

I've got two sets of Dlink's DHP-301 and they're fantastic. (It was the first product I'd bought in a long time that 'just worked'). Most adapters also support encryption if you're worried about anyone watching the traffic since you might be on the same electrical circuit (I don't remember what exactly its called).