I have been playing with *Spark for about a week now and I have to say the concept is good, but the execution is on the weak side.
*Spark is a custom launcher (think ADW, LauncherPro, Slidescreen). The app seems to work well, as intended, according to the video of how to use the app on their site http://sparkmyphone.com
*Spark gives you immediate details on your Twitter and Facebook streams, it also pulls and shows the latest headlines, and the weather. There is also a shortcuts option, but it is pretty worthless.
The home screen is nice to look at and has some odd navigation quarks, dragging will highlight a part of the screen (which I always worry will translate to a click). The home screen gives quick access to the other modules of *Spark as well by clicking each module.
Once in a module the content is presented in a list style (headlines separated by topic). Clicking on any topic/post will open the links contained within.
I would have preferred *Spark to open my Twitter app or Facebook app instead of opening a web browser, and I saw no place to adjust this setting. So get used to using the Facebook and Twitter mobile sites instead of your native applications.
Headlines I find to have some horrible selection in articles, and is limited to approx 10 in each category, which is hardly enough to make it worth using.
*Spark has a "Post your status..." box, unfortunately it doesn't play well with Swype input, requiring the user to type out each word instead of Swyping. This is the only application I have come in contact with that has this sort of problem, and sadly it is not limited to the Status updates, all fields in *Spark suffer from this. Also backspace/delete doesn't work at all with Swype, so if you mistype a char, you have to start over.
The app drawer provided by *Spark is also an point of annoyance. Although the wrap around panels is nice, having no sign of a drag until the screen changes is really hard of users. You aren't sure if you are swyping or clicking until the next screen appears.
Overall the app has HUGE potential, and I will certainly be keeping an eye on it as it is the type of home screen I prefer, it just needs to spend some more time with the SDK and get things flushed out so use is more natural feeling, and stop sending me to the web for all my content that is local.