My only concern is convention or just plain habit. Even though you may find oldstyle the one you would most often use, people are accustomed to seeing lining figures as the default and your way might confuse them. If they have standard style sheets with lining figures used in tables, they can change only the font in the style sheet and get the expected result. If they use your font, they don't get what they expect.

Figure style is a big part of the personality of a typeface. If you think oldstyle figures are the ones most in keeping with the style of your font, I'd go ahead and make them the default.

It's OpenType, so people can change the figure style to suit their preferences. The only real disadvantage is that only the Adobe apps make it easy to select figure style right now, so people who want to use lining figures might curse you, but that goes both ways.

Paul,

I think Chris mentions the major concern -- people are used to seeing lining figures. Minor concerns are what would happen when users attempted to typeset math, and what would happen with tabular figures. If it's an OpenType font, and you include the other figure types, users could just choose what they want. When I convert my OpenType fonts into TeX fonts, I always use onum for the default fonts because it's what I want. But I also make lining "versions" because I'll be using those in mathematical expressions.

Forrest,

TeX and friends can use figure styles (or any other OpenType feature) without any problem. I use 'otftotfm' to make a variety of different Type 1 fonts that I use in my TeX documents (one with lining figures, one with discretionary ligatures, etc.). In fact, I'd imagine you could use the same tool on any platform to extract whatever Type 1 variants you want. It's not quite as convenient as choosing the feature from a menu in InDesign, but it's also not a huge problem.

Chris Swingley, Fairbanks Alaska