According to comScore, Google+ has over 20 million users, not including those who visited the Website from Android or smartphones. Of them, 5 million users were from United States.

It took merely three weeks for Google+ to attract this many visitors. It is more impressive given that access to Google + is by invitation only, meaning people can join only if a current member invites them.

As of July 19, comScore showed Google+ at just about 20 million visitors worldwide, an extraordinary number in just its first three weeks, said Andrew Lipsman, vice president of industry analysis at comScore.

United States leads in Google+ audience; India is No. 2 with 2.8 million visitors. The U.K. has (867,000 visitors), Canada (859,000 visitors) and Germany (706,000 visitors) rounded out the top five. In fact the number of visitors that may be even higher comScore didn't count visitors from mobile phones, such as the iPhone and Android smartphone users.

Also, comScore did not take into account Google+ usage through the Google+ tool bar that rests atop most Google pages these days. While Google + was successful to attract lots of visitors initially, the real challenge is to keep these people active and engaged.

Also, there are complaints among business users that Google+ has failed to serve their needs.Google didn't anticipate the huge demand from business user's demand to use Google+ as promotional tool. 

However, Google+ has gathered good enough attention and pulled off a good number of visitors to its new service to have a chance to compete with its rival Facebook. But still has a long way to go to reach the scale of Facebook Inc., which has more than 750 million users, and Twitter Inc., which has more than 200 million registered accounts.