All test performed on a Pentium G630 (Dual-core Sandy Bridge, no AES-NI).
The working directory is on tmpfs.
The untar test uses https://cdn.kernel.org/pub/linux/kernel/v3.0/linux-3.0.tar.gz .
The archive is placed on tmpfs as well.

WRITE: dd if=/dev/zero of=zero bs=131072 count=2000
READ:  dd if=zero of=/dev/null bs=131072 count=2000 2>&1
UNTAR: time tar xzf ../linux-3.0.tar.gz
MD5:   time md5sum --quiet -c linux-3.0.md5sums
LS:    time ls -lR linux-3.0 > /dev/null
RM:    time rm -Rf linux-3.0

(or just run benchmark.bash)

VERSION           WRITE    READ     UNTAR  MD5   LS     RM    ENV CHANGE?
v0.4                                48          1.5    5
v0.5-rc1                            56          7     19
v0.5-rc1-1                          54          4.1    9
v0.5-rc1-2                          45          1.7    3.4
v0.6                                47          1.8    4.3
v0.7                                43          1.7    4.3
v0.7.2                              26          1.8    4.3
v0.8                                23          1.8    4.3
v0.9-rc2           94               24          1.8    4.5
v0.9               94               24          1.8    4.5
v0.11             104               22          1.7    4.5
v1.1              104               20          1.5    3.4    go1.7.1
v1.1.1-34         112               22          1.5    3.6    go1.7.3
v1.2.1-33         112               21    12    1.6    4.4    go1.8
-serialize_reads  116               21    39    1.5    4.4    (v1.2.1-33 with -serialize_reads)
v1.3-27           113               20    11    1.4    4.2
v1.3-53-gf44902a  119               19    12    1.6    4.1
v1.3-64-g80516ed  123               19    11    1.3    4.2
v1.3-67-g9837cb0  125               19    11    1.4    4.2    go1.8.3, Linux 4.10
v1.3-69-ge52594d  145               19.0  11.6  1.4    4.1
v1.4-1-g3c6fe98   154               17.2  11.7  1.4    4.1
v1.4-5-g0cc6f53   182      144      16.7  11.1  1.3    3.3
v1.4-8-g80676c6   178      148      16.1  11.0  1.3    4.0
v1.4-14-g9f4bd76  182      286      15.4   7.5  1.3    4.1
v1.4-45-gd5671b7  183      282      14.9   7.3  1.1    2.9
v1.4-45-gd5671b7  252      285      15.5   7.2  1.1    2.9    go1.8.3, Linux 4.11
v1.4.1            253      285      16.0   7.4  1.3    3.0    go1.9,   Linux 4.12.5
v1.4.1-6-g276567e 258      289      16.1   7.5  1.3    3.0
v1.5              228      292      17.6   9.3  1.5    3.5    go1.10.2, Linux 4.16.8
v1.6              250      289      17.7   8.0  1.3    3.2    go1.10.3, Linux 4.17.12

Results for EncFS for comparison (benchmark.bash -encfs):

VERSION            WRITE    UNTAR   MD5    LS     RM
encfs v1.9.1       95          20     8    2.8    3.8