Another point: if there's any temporal locality to your future access patterns - if you're more likely to access multiple rows which were inserted at roughly the same time - then allocating sequential identifiers brings those entries closer together in the primary key index.

I used to work on a reconciliation system which inserted all its results into the database. Only the most recent results were heavily queried, with a long tail of occasional lookups into older results. We never had a problem with primary key indexes (though this was in MySQL, which uses a clustered index on the primary key for row storage, so it's an even bigger benefit); the MD5 column used for identifying repeating data, on the other hand, would blow out the cache on large customers' instances.