I have been using Google App Engine for two years. I don't remember the version of the solution.

We are a Premier Partner of the product.

I have been using Google App Engine for six years. My company has a partnership with Google.

I have been using this solution for about seven years.

I've been using this solution for three years. 

I've been using this solution for the past few months. 

I have used Google App Engine for three months.

I have been using it for two and a half years.

I have been Google App Engine for approximately four years.