3 shots of the same subject from today using 3 different B&W presets showing the effect of each.
1) Soft B&W. It is soft, low-ish contrast...easy to get a landscape in DR even on a high contrast day like today was. I like this one for land/seascapes and it would probably be nice for portraits.
2) Hard B&W. Much higher contrast with a lot of what LR would call structure. It's more of a struggle to prevent blowing highlights - I use highlight priority exposure mode and the result is deep shadows, or to use exposure comp to blow highlights (or dig into options to boost shadows). You can also see some fairly obvious sharpening artefacts as a result of the structure boost, but this could be dialled down a bit if you wish. This would be better suited to street, but it's nice for gritty sinister looking landscapes.
3) Hi Contrast B&W. Deeper and harder contrast. Almost impossible to prevent blowing highlights without rendering shadows in silhouette. This is the only preset that the 'grain' option is enabled - this option can't be turned on or off at will, only by selecting the preset or not. This is a little disappointing, I would like to select it when I want and I would like more control over the amount and type...hopefully that will come in future.