I've been riding with this jacket every day for the past 3 weeks, through 70-80 degree days and 30-50 degree nights.
I will say that the "windproof-waterproof liner" is effective, but when you're getting below 50 degrees this jacket has so much airflow that you absolutely will need to layer a little bit. I wear a thermal shirt and a long sleeve shirt underneath it and I am comfortable down to about 35 degrees.
I would say this jacket is great for anything down to around 45.
The armor in this jacket is snug and is positioned exactly where it should be, it is very comfortable and you really don't notice it at all.
Being that it's a summer jacket the cuffs are also very slim, so fitting a gauntlet glove over them is quite easy, but fitting one underneath the cuff would be difficult.
Overall this jacket is exceptional for anything above 40 degrees, has great armor protection (room for a back protector as well !) is very lightweight and extremely comfortable. I would say all of the information posted by Revzilla is quite accurate and this is really a spring summer fall jacket (at least on the west coast).