Hi Rich,
It is true that the ORDER BY clause supports ascending and descending; unfortunately it executes slowly. Especially for large result sets, it is much faster to index the output by using INDEX ON rather than ORDER BY.
To tell the truth, I haven't benchmarked this since the early days of SQL in FP2x, but I don't think anything has changed. FP's SQL-Select is blindingly fast, but the same is not true (or was not true) for the ORDER BY clause.
You could benchmark the performance difference if you need to be sure about this. I try to avoid ORDER BY except for small result sets.