First, here's the 'old' FSX, without the ENB tweak:

To me, this just looks 'flat' now, as the whole range of light values is scrunched into the middle range. In reality, the brightness range is far greater than anything the monitor can display, so it's nice to have some attempt at reproducing this:

Although the ground textures are changed quite a lot, the main use for this is in the sky, of course. The most important area for me is towards the horizon, where the blue bloom effect is much more pronounced.
One thing which you need to take into account is the rather simple way this thing works. It doesn't know what is sky, of course, so it needs to take a few guesses. To do this, it assumes that the sky is up, which isn't always the case. You will notice a change in brightness as you look up and down.
Here's our test shot, without ENB:

And with ENB:

I've chosen to look up a little, as this stops the ground from going too dark.
If I look down, you can see that it gets a bit overpoweringly gloomy:

And looking up further, the ground gets brighter again:

The only time I need to turn this off is at night (although it is possible to tweak the night settings, I just haven't done it yet), sometimes if I get close to the snow (such as landing a heli in the mountains) or trying to find a landing spot looking down into a dark forest/lake -- it all gets a bit difficult to see, so I 'cheat' by switching ENB off for a bit.

