How about 114 (including the 'du -k|':

df -k|perl -ape'map{while(1024<$_){$_/=1024;$i++}$i="%6.1f".substr"KMG
+",$i,1;$_=sprintf$i,$_}@F[1..3];$_=join"\t",@F,$/'

[download]

Output using the sample data looks like this:

/dev/dsk/c0t1d0s1          1.2G  795.7M  382.2M 68%     /usr
/dev/dsk/c0t1d0s3        239.7M   43.5M  172.2M 21%     /var
/dev/dsk/c0t1d0s0        414.6M  182.8M  190.3M 49%     /home

[download]

I didn't come up with a way to cleanly format G to 1 decimal place, leaving K and M at a whole number (ie 1.2G, 240M).

94 if less precision and un-aligned formatting meets your standards :-P

df -k|perl -ape'map{while(1024<$_){$_>>=10;my$i++}$_.=substr"KMG",$i,1
+}@F[1..3];$_=join"\t",@F,$/'


Output:
/dev/dsk/c0t1d0s1       1G      795M    382M    68%     /usr
/dev/dsk/c0t1d0s3       239M    43M     172M    21%     /var
/dev/dsk/c0t1d0s0       414M    182M    190M    49%     /home

[download]

Update: fixed miscounts

In reply to Re: A little golf anyone? by jsprat
in thread A little golf anyone? by deprecated

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.