A-gps isn't a total solution. It doesn't impact the sensitivity of the GPS, it provides a shorter list of satellites to search for and will by definition help some. There are a number of factors that can impact the fix time. I believe satellite communications works best line of sight. The odd tree could impact it. I wouldn't rule out driver changes but the issues are more likely the chip set itself or perhaps the antenna design. If the 1st GPS fix time is that important you, there's the option to purchase a separate bluetooth GPS receiver.