My background is in black and white though I now do half or more of my work in colour, thanks to shooting digitally. I thought that for those of you who predominantly work in colour, I might point out some reasons to at least occasionally work in black and white.
1) some images just don't work in colour because the colours are wrong or an object sticks out like a sore thumb
2) some images just look better in black and white - you might just want to convert some and see. In Lightroom and Camera Raw and Photoshop this is easy.
3) Black and White prints last longer - whether silver or inkjet. The black in inkjets is carbon which is about as permanent as you can get so printed on a good art paper, should last hundreds of years.
4) Black and White isn't real. You'd think that might be a disadvantage but when you want to create artwork, you want to dissociate yourself from the reality of the scenery and black and white is very effective at that. Colour risks looking too much like a postcard.
5) Black and white images can be highly manipulated and still look good. Colour manipulation taken too far looks unreal and therefore disturbing. Black and white was unreal to start with which was expected so going further isn't an issue.
6) Black and White can be wonderful for portraits and nudes. You can use colour filters to alter the skin to look darker or lighter (green or red filter).
7) A good black and white print can have a richness that is magical and can't be reproduced in colour. Can you imagine Pepper # 30 in colour? Horrible!
8) Black and white prints don't have any colours that will clash with your living room paint - trust me - it's easier to decorate with black and white.
9) Black and White is just different - we live in a world of colour - most of the images we see, whether in magazines, on the net or on television are in colour - sometimes it's just a nice change to look at black and white.
10) some subjects lend themselves well to black and white - they don't look so damn cheerful as can colour images.
If you are shooting digitally, don't forget to photograph in colour and do the black and white conversion after the fact so that you can 'filter' as desired in computer. There are no advantages to setting your camera to black and white except one - if you use a consumer digital camera rather than dSLR, then the LDC will show you what the black and white images are going to look like - but in general it isn't worth it and doesn't work with most dSLR's except after the fact.