using hash index when BETWEEN is specified

I has played with new hash index implementation and I tried following 
command:

postgres=# select * from test where id between 1 and 5;
Time: 9651,033 ms
postgres=# explain select * from test where id between 1 and 5;                       QUERY PLAN
--------------------------------------------------------- Seq Scan on test  (cost=0.00..141681.00 rows=1 width=4)
Filter:((id >= 1) AND (id <= 5))
 
(2 rows)


Hash index is created on id column. However when I use

postgres=# explain select * from test where id in (1,2,3,4,5);                               QUERY PLAN
------------------------------------------------------------------------- Bitmap Heap Scan on test  (cost=22.24..332.53
rows=83width=4)   Recheck Cond: (id = ANY ('{1,2,3,4,5}'::integer[]))   ->  Bitmap Index Scan on test_idx
(cost=0.00..22.22rows=83 width=0)         Index Cond: (id = ANY ('{1,2,3,4,5}'::integer[]))
 
(4 rows)

Time: 1,352 ms

I'm not planner guru but it seems to me that BETWEEN clause could be 
rewritten as a IN clause for integer data types and small interval.

    Zdenek