When creating a chart in Calc, the data groups are very restricted,
making it completely impossible to use Charts in some cases.

1) You can not specify a data group independent of other groups.
For example, if you have two sets of numbers, one set being a
column, say A1:A10 and an other set that us a row, C5:I5, you can
not put them into charts as 2 sets of data.Chart will create many
sets of data, depending on whether you specify column or row ordering.

2) You can not specify data sets which are not a continuous region
of a column or row. You can not, for example, tell chart that you
want A1:A10;C3:C8 to be drawn as *one* set of data.

3) If you have XY chart, you can only have one X value set. 
You can not create a chart where the X values for two (x,y) 
point sets (that is, for example 2 sets of measurements)
are not the same. You can not tell chart that A1:A10 are the
X values for the first function, B1:B10 are the Y-s, C1:C10
the X-es for the second function and D1:D10 are its Y-s. If you
specify the range (A1:D10), Chart will treat A1:A10 as X values
for 3 functions, in the columns B, C and D respectively.
This means that you CAN NOT create a scattergram for comparing
objects at all, rendering Chart useless for a lot of scientific
publication purposes.

4) If you have an XY chart, even if it is just one function, Chart
insists that the X values are sorted. That means that you can not
use Charts to plot a 2D parametric function, quite often used in
scientific and engineering publications and/or work.

Both Excel'97 and ApplixWare allows you to individually set up
data groups. A data group can be any combination of of cells,
you can even list completely independent cells if you want, like
A1;C10;B3;A9;F33;D7 and so on.
For XY charts both programs allow you to set up independent (X,Y)
sets, the only restriction that within any given set the number
of X values must be the same as the Y's. For example, it is
perfectly legal:
Group1
X A1:A4;B3:B7
Y F4:M4;C3

Group2
X G7:G20
Y M7:M20

and the first set has 9 (x,y) points in it, the second one 14.

I addition, there is NO restriction on the X elements, they can be in
any order, so you can plot a circle, a spiral or whatever else you
happen to calculate with Charts.

The above functionality I believe is fundamental and if Chart can not
do that, it indeed is a defect, not just a missing feature. It is a
complete showstopper for scientific applications. Non computer-scientists 
like biomedical ones tend to calculate and plot everything in Excel and
they *need* scattergrams, foldback XY charts and arbitrary data groups.
They will not buy into OO if they can't do that any more.

Not a showstopper, but a feature nevertheless, that whether a data group
is shown as dots only or lines or curves etc. can be set on a group by
group basis in both Word and Applix. It is a feature sometimes useful
for scientific/technical work.

Zoltan