As an FYI, Amazon has this product listed 3 different ways as "Motorola Surfboard Broadband Cable Modem SB-5101" and as "Motorola Surfboard SB5101 Cable Modem" and as "SURFboard Cable Modem". All are listed at 3 different prices, too!
I did a little bit of homework, and the Motorola seemed to have good reviews. This product is supposed to be the same in function as the SB5120 except that the SB5101 uses a slightly different chip set.
I chose to buy a cable modem so that I could replace the rental unit from the cable company. Make sure your cable company supports this cable modem before buying!
For my setup, I have my cable service from the evil Comcast, my cable modem, and an older Linksys wireless router. The day my Motorola cable modem arrived, I took it out of the box, glanced at the Quick setup guide, and plugged it in. I called Comcast, navigated through their Byzantine automated phone menu system, and read off the MAC ID to the tech services person. He did some stuff on his end to first recognize the new cable modem. Then he had to do some other configuration on his end because of the router. Once that was done, viola! We've been using the cable modem for the past week or so without incident.
To me this is the best kind of electronics product. It takes ~30 sec to hook it up, and once it's done, you can forget about it. It took longer to open the package (and much longer on the call with Comcast) than it took to hook it up.
I've had a Motorola 5100 for about four years. It gradually got degraded and these, like all electronics, wear out and need to be taken out of service. So I bought a new 5101.
The switch was very quick and easy. I called Cox and gave them the information they needed and was online fast.
Let me tell you --- the Internet really flew! I can't tell you how thrilled I was. It made all the difference in the world.
I have a wireless network and a Linksys router. I switched out the router and modem at the same time. The speed on all my computers increased greatly and I no longer have dropped connections.
I depend on my computers for my phone calls through Skype and for my entire business. So I have to have the best and fastest, the most dependable.
I highly recommend this modem. It's reasonably priced and lasts a long time. But do keep in mind that all modems will need to be switched out at least every two or three years if you want to stay on top of things.
Update: I have learned that a number of ISPs like people to use this modem because they can block certain ports of those people who do. This may not be a problem for you. But for some people, it can be. Before you buy it, look around the web and make sure it's what you want. Cable people will deny they do this, but they do. And it can really mess up your Internet experience and give you lots of trouble.
SURFboard SB5101 Cable Modem 515290-107-00