Many degrees of fascination and utility in this, some more potential than actual at the moment. For me, the big feature is the time-line, which makes this a history research tool of sorts. You can skip back and forth in time, move the selection window around, and of course refine your query. You also have a choice of returning images. The results are currently drawn mostly from Twitter, occasionally also from Facebook, with associated images then coming from a variety of sources, including flickr, myspace, twitpic, tweephoto, etc.
I was surprised at the potential I see here, particularly as I'm not a big twitter fan. (I don't personally like that kind of fragmentation of my attention). And yes, unfiltered Twitter quality is pretty questionable. I'm sure Google has in mind various reputation-weighting scenarios for social media, but I don't know that they're here yet.
Over time, real time search might become a tool for studying the propagation of trends, the consequences of events, the sources of rumor, and the nature of the social fabric. (It's also useful, as noted, for finding yard sales and the location of taco trucks). Most likely, the data will be more valuable for computer analysis than for manual analysis... but it's unlikely we'll get access to the data at the bulk level. There are of course sinister implications as well as benign academic uses.
The scrolling display reminds me of the constantly scrolling display of real time world searches at the Googleplex. It's a fascinating window into humanity. You watch it for a while, then shake your head in amusement or astonishment or dismay, and eventually turn to other things. Or, like Google, you can study it seriously.
There's a similar fascination here, focusing on the social data stream one query at a time, with some queries much more interesting than others. I'd like to see the sources broadened and weighted, and the refinement tools enhanced. Ultimately, I'm sure we'll get something like Google Realtime Trends, which will give us some smoothed out data for top searches.
I'd like to see Google take realtime results off the regular serps pages unless they're especially compelling (as with a breaking news story), and develop this tool further.