Not very at the time, but that is mostly due to expense. With so many nanotech companies still in the teeth cutting process, production is prohibitively expensive. Over the years as more companies come about and ways of creating it get better/more efficient, you'll see the process come down by a LARGE amount. And with the relative abundance of raw materials needed for it to be made, I would guess that in the end it will be LESS expensive.

For actual usefulness, it's a far better conductor. 100x faster by some reports...and the obvious benefit that it is effective in sheets 1 atom thick...

http://www.tomshardware.com/news/graphene-replace-silicon-day-scientists,5075.html
"College Park (MD) - Researchers found that electrons can travel substantially faster in graphene than in silicon, a standard material used in semiconductor products today. The fairly new material is believed to accelerate the electron flow by a factor of 100x and bring big advantage for applications that require rapid switching."

http://www.sciencedaily.com/releases/2007/09/070914144009.htm

http://www.edn.com/article/CA6545125.html
"With semiconductors, a different measure is used to quantify how fast electrons move – mobility – with the limit to mobility of electrons in graphene set by thermal vibration of the atoms of approximately 200,000 square cm/Vs at room temperature, compared to about 1,400 square cm/Vs in silicon, and 77,000 square cm/Vs in indium antimonide, the highest mobility conventional semiconductor known."