I love my Slingbox! I have a Slingbox Classic that I bought from Woot over three years ago, and I’ve been using it ever since.
There are a lot of TV streaming products out there these days, with varied capabilities. I think a major strength of the Slingbox is the mature, high-quality software that comes with it. Over the years they’ve made great strides with Slingplayer on Windows, adding scroll-back to pause or replay live TV and an integrated program guide. There’s also the “SlingBar” window sizing option, which “docks” the player at the left or right edge of the screen and keeps maximized windows inside the remaining space. It’s great for watching TV while you work, and easier to set up than any TV tuner I’ve used.
The Mac version is a bit more primitive and lacks the aforementioned features, but it works fine.
Windows and Mac versions both allow you to letterbox/pillarbox the video as needed. I use this a lot on my widescreen netbook to remove black bars from some shows on SD analog cable and fill the screen.
SlingPlayer Mobile has been out for Blackberry for a very long time, iirc, and more recently they’ve come out with versions for Windows Mobile, iPhone, and most recently Android. The Android version is $30 and came out just last summer; I don’t know what the cost is on other platforms.
I lived in a dorm until a few weeks ago, so the internet connection there was awesome for streaming over the internet. I was expecting to have problems when I moved back home, due to the poor upstream speed of cable internet. So far, though, there haven’t been any issues streaming over the internet to my phone or my laptop. The Slingbox will lower the quality of the video if the network bandwidth isn’t high enough, but I haven’t noticed any noticeable difference as of yet.
EDIT: Oh, do note that this one can’t tune a cable signal; you need a Slingbox Pro or a Slingbox Tuner for that. This one is ideal for use with a set-top box or DVR, though.
Edit 2: Some people have gotten the Windows version of Slingplayer to work on Linux under Wine. It didn’t work so well for me; YMMV.