Am 17.11.2013 um 15:33 schrieb honyk :

Other OTF features needs to be declared though: \definefontfeature[f:superscript][sups=yes]

and then used as written above: 25 m{\feature[+][f:superscript]2}

But it is not so big deal.

When you use this for units you can use the \unit command: \starttext \unit{25 square meter} \stoptext

<joke>I suggest removing all font styles related descriptions in manuals, wiki pages to some special place marked as obsolete and replace it with this simple approach ending with a small note that if this is not applicable, there are other, but deprecated, ways - with the appropriate hyperlink.</joke>.

Not all font provide small caps as font feature, there is still many (older and newer) which use a separate file for them. Wolfgang