Question about :what is a reasonable time for a transform?

I am transforming an XML file of ~70 000 lines into a file of ~100 000 
lines using XSLT, and also doing the reverse to reconstitute the 
original file. 

The amount of actual data in each node only takes about a line, so a 
reasonable estimate of the number of nodes could be (number of lines)/2.

The initial file has a depth, on average, of about 4. The resulting file 
is essentially flat, all nodes are in the root node.

Using Saxon 6.5.4, the forward transform is taking about 20 seconds. The 
reverse transform (from essentially flat to the nested structure) is 
taking about 200 seconds. I am performing the transform in the Oxygen 
xml editor - which probably implies a little overhead - on a Mac G4 
1.25GHz.

Questions:
Do these times seem representative for this file size?
Is the asymmetry between (nested -> flat - I mainly use the intrinsic 
recursion) and (flat -> nested - I mainly use for-each) to be expected?
Would xsltproc be quicker, or some other tool?

many thanks

shaun