From Bryan Eisenberg at ClickZ:

Just six months ago, personas were little more than an industry buzzword. At the recent AD:TECH conference, I surveyed the room a colleague was speaking in and was pleasantly surprised to find 30 percent of the audience claimed to use personas in site design.

Now that persona use is more widespread, the questions are different. No longer do people ask if they should use personas. Instead, they ask if their personas are effective.