Multi-level .ix works on Series but not on DataFrame
Using pandas 0.10.1.  The .ix on a multi-index Series seems very inconsistent with the .ix on a multi-index DataFrame. 
# From page 147 of Wes's book:

data = Series(np.random.randn(10),   index = [['a','a','a','b','b','b', 'c','c','d','d'],  [1,2,3,1,2,3,1,2,2,3]])
data.ix['a']  #works as you'd expect, pulls all the 'a'
data.ix[ : , 2 ]  #works as you'd expect, pulls all the '2'
# Now the exact same thing except use DataFrame instead of Series.

data = DataFrame(np.random.randn(10),   index = [['a','a','a','b','b','b', 'c','c','d','d'],   [1,2,3,1,2,3,1,2,2,3]])
data.ix['a']  #works as you'd expect, pulls all the 'a'
data.ix[ : , 2 ]  #ERROR! But why? It works for series.
# Also there is...

data.ix[ 'a' , 2 ] #works on both DataFrame and Series
data.ix[ 'a', : ]  #works on the DataFrame but ERROR on the series. (Though easy workaround is just .ix['a'])

I'd sure expect the .ix[]  to work the same way on DataFrame and Series. Is there any reason they don't? Can we change it so the dataframe has the same functionality as series?
