Yeah, I was hoping for extension properties too:

public static TimeSpan Minutes[this int i]
{
   get { return new TimeSpan(0, i, 0); }
}

public static DateTime Ago[this TimeSpan ts]
{
   get { return DateTime.Now.Subtract(ts); }
}

So then I could do:

DateTime d = 20.Minutes.Ago;

No ugly parentheses!