New Lens Happiness
The f4 40-150 is a winner in every sense.
The f4 lens runs the risk of replacing both of my other 40-150 lenses. It is not noticeably heavier than the plasticky kit lens and the consistant f4 through the range is handy. It is substantially lighter than the f2.8, as sharp, as fast in focussing and at least as weather proof. It is also $1000au cheaper to replace.
Apart from the performance difference between it and my copy of the 35-100 Pana lens I have respect for, but suspect I got a low end copy, the lens is delivering very much the same performance as my f2.8 with only the one stop of difference.
The reality is one stop is actually not that much benefit.
As a rule, if f4 is not fast enough at all, probably f2.8 will not make enough difference (an extra ten minutes in fading light or a slightly higher success rate with a still too-slow shutter speed). I find that f2.8 for me is simply a matter of depth of field control. If I am struggling at f4, I will likely switch to f1.8, because in most cases I can.
This lens and my 75 f1.8 have a combined weigh and cost that is less than the f2.8 zoom, so overall better options.
The f2.8 will be the one lens option for sports under lights or smaller fields, the f4 zoom for brighter light and the 300 for larger field sports. For indoor sports, I will turn to the f1.8 primes.
For travel, the kit lens is still king, because weight and replaceability are all important when travelling.