[ubuntu-uk] Pasting home directory into new and version upgrade installs?

[alan c]

I have a friend with Ubuntu 9.04 and I will do a version upgrade for 
them soon. One option is to version upgrade online to 9.10 and then, 
at another convenient future date,  version upgrade to 10.04 LTS, 
which they will stay with for a longer time.

Another option is to do a clean reinstall of Ubuntu 10.04.1 LTS now, 
and then re-configure to match the user's apps and data.

One suggestion I have received is, that after a clean reinstall of 
10.04.1, I could then replace the clean /home/username directory with 
the copy of the directory from the user's 9.04 which I would have 
created earlier in careful backups.

Thinking of this last option, I find a number of questions come to mind.
What is the effect of brutally just replacing /home/username from an 
earlier version, possibly two or so versions old? The user has one app 
for example, Digikam (in Ubuntu) which they regularly use, and this I 
guess uses a number of kde libraries whatever.  I cannot help 
wondering what sort of clean up  (or chaos) I might be faced with, 
perhaps out of my depth too, by following this latter approach.

I would welcome comments here.

tia
-- 
alan cocks
Ubuntu user