I've found that dealing directly with hardware and reading registers yourself can be tedious and frustrating, especially when it's difficult to find reference points (testing lux is definitely one of these times, as someone across the 'net may have several 1kW bulbs burning, but their bulbs may have x, or y, or z or any number of other spectrum-diffusing things happening).
I'm glad the recommendation for an app helped. After my units arrive, I'll drum up some code being non-biased, and we can compare some numbers (again though, I'm sure my light source'll be different from yours. However, there's always one that is pretty consistent ;)
I often write C against my Arduino that has analog inherent, then translate the C code to something I can provide a Perl API for, so I get results on two separate platforms (for instance, my ADCs/dpots I test against the Arduino, then port to the Rasperry Pi). I'm looking forward to getting these units so I can have someone live-time to compare numbers with and discuss.