In my box in isql mode ( win7_x64, dedicated ssd drive for databases)
default db configuration

is still difference between 2.5 and 3.0:for select first 1000000 *
(now over 100% of time fb 2.5)


//2.5
SQL> select count(*) from t1;
Current memory = 34646136
Delta memory = 0
Max memory = 34728928
Elapsed time= 4.44 sec
Buffers = 2048
Reads = 37865
Writes 0
Fetches = 20075721

SQL> select first 1000000 * from t1 order by id desc;
Current memory = 34647216
Delta memory = 1080
Max memory = 96519656
Elapsed time= 22.34 sec
Buffers = 2048
Reads = 37869
Writes 0
Fetches = 20075727


// 3.0
PLAN (T1 NATURAL)
Current memory = 19336792
Delta memory = 250752
Max memory = 19410568
Elapsed time= 5.143 sec
Buffers = 2048
Reads = 80764
Writes = 0
Fetches = 20161661
SQL> select first 1000000 * from t1 order by id desc;

PLAN SORT (T1 NATURAL)
Current memory = 19338432
Delta memory = 1640
Max memory = 91705160
Elapsed time= 55.905 sec
Buffers = 2048
Reads = 80701
Writes = 0
Fetches = 20161347


--
regards,
Michał Kurczabiński