Yes, it may make your screen look a little orangey at night and this may take a few minutes of getting used to, but it's well worth it.
The developers behind f.lux have collected research on how using f.lux can benefit your sleep and this can be found here.
However, to summarise the research listed, it is claimed that "blue light in the morning" treatment is a popular treatment for people with sleeping disorders. F.lux allows for this by increasing the color temperature at sunrise.
It is also agreed that it is best to avoid blue light within two hours of sleep. This is because it is commonly thought a high color temperature at night prevents us from sleeping for "roughly an hour and sometimes more".
Furthermore, f.lux prevents eye strain as warmer colors are far less harmful to eyes late at night.
It's very possible to see these effects yourself.
After you've downloaded f.lux and set it up, which takes all of a few minutes, you simply have to sit and wait.
Once it's been a few hours past sunset and your screen has changed to a much warmer color, disable f.lux.
I've yet to see anyone not be shocked as to how bright their screen now becomes and since then anyone I've known to use it has continued to do so - and you should too.