We just finished upgrading our solar setup today and I'm working on writing a detailed article about it soon. In short, it's a but more complicated than it first looks. The controller is key. Basic ones that come with the kits are PWM controllers, which do not allow you to get the maximum usage out of your panels. An MPPT is MUCH better but also much more expensive.
We used the 60 watt kit for a little over 3 years. Because of the way the controller works, we estimated the system have us about 24-30 watts an hour during peak sunlight. The new system is 100 watts and so far today - with clouds, dust and haze - we're getting about 70 watts an hour. Full sunlight will likely put us very close to or at 100 watts. HUGE difference and I'm thrilled
I'll try to post more details in the next few days as I have time.