I'm not a big fan of that format syntax. It's just hard to look at and figure out what went wrong when things do go wrong.
I'd prefer something like: https://gist.github.com/963027 But someone would have to implement it, of course. I have my own little echo() function which takes simple "{}" positional syntax, it doesn't have any other formatting options though. But I only ever need formatting for simple cases like the above. It seems some people need a whole word processor macro language embedded in a format string..