I always used gravel until recently when I was upgrading to a 4ft tank. I decided to go with a mixed substrate - so I have sand at both ends curving around, with the middle section in gravel, with large rocks, pebbles and plants separating the sand from gravel areas.
The sand was absolutely a doddle to use (and cheaper than gravel!) - I took the advice from the majority on here and bought Argos Play Sand - it took very little time to clean it (I put it in a bucket, on the lawn and let the hose run into it on a gentle flow, stirring it up now and then to release any dust (but it was very clean after the initial few minutes of scum washed away). After about 10 mins it was crystal clear.
Put it in the tank (don't worry about styling how it looks as it will change once the water goes in) - filled the tank slowly over a plate - no cloudiness whatsoever! The sand barely moved.
Argos sand is a beautiful light sandy colour, which is perfect for tropical aquariums.
I then used a long skewer to poke and lightly stir into the sand to release trapped air bubbles (lots!). Then you can "style" it - some have their sand flat, others have dunes. I did mine with a few low dunes but since then my convicts have totally changed the way it looks by nest building in it so I have higher dunes now and it looks kind of wavy from the front and a bit more natural!
I can honestly say it is super stuff. Not sure if it's because of having a good filter or what, but after a week I don't see any detritus on the sand at all so I've had no need to use the gravel vac on it yet.
Definitely wish I had used sand earlier in other tanks and will definitely recommend to others if that is what suits their fish.
Here's a pic of one third of my tank to show how the sand has been shaped by my fish:
Regards, Athena