Hardware: the absolute minimum
There's no use looking for any accessories or flexibility: you won't find anything, apart from the ability to tilt the screen back by a few degrees. You'll also have to make do with just VGA and DVI inputs, which leaves the S231HL with just one star in this section.
Responsiveness: a pleasant surprise for a 5 ms TN
There are dozens of 5 ms monitors out there, and it isn't very often that they surprise us with their responsiveness. That's what the Acer S231HL managed to do though. It's not as fast as a 2 ms screen, but its results leave it firmly between the two categories.
In reality, that means that fast-moving objects are displayed slightly more smoothly than we'd expect on a monitor that's reserved for office work. It's still not responsive enough for us to actually recommend it for gaming though.
And as for the input lag, the gap between the signal leaving the graphics card and actually appearing on screen, there's nothing to worry about: it's so short in this case as to not be noticeable.
Colours: skin tones look purple
Compare the Acer S231HL to other monitors in our Product Face-Off
With its default settings, this monitor produces colours that have a strong blue tinge. Flesh tones, meanwhile, have an annoying tendency to look purple. We would normally correct this sort of problem by adjusting the colour temperature mode from 'Standard' to 'Warm'—except that the S231HL is already set to 'Warm' when it leaves the factory.
The good news is that you can switch to 'User' mode and correct goings that way. You need to set red to 50, green to 29 and blue to 28. The bad news is that things still aren't perfect, and the deltaE, or discrepancy between the colours requested by the graphics card and those shown on screen, is still mediocre. To make sure you get a decent display, you'll have to download a calibration profile.