I just upgraded from 1.80 to 1.90. I noticed that all of the Full Descriptions were truncated. This happened once before and I am unsure if I noticed it after a 1.50 to 1.80 upgrade. The upgrade may not be the cause.
My products are singe variant, so I used the Full Description on the Product Details Page, not the Description on the Variant page.
I cannot say for sure that they were intact before the upgrade, but I do know they were there. I used the standard upgrade script.
Since all of the descriptions were truncated it had to be one of two actions. The upgrade or an export/import to/from Excel 2007. Those are the only two actions I performed that was on the entire database.
Over the next couple of days I will create a test 1.80 system and do an upgrade to 1.90. I will post the results.
i expect it was truncated by excel exoprt ( I think the issue was fixed by v1.9)
You don't need to export your products before an upgrade - the existing database is updated leaving your data intact
if you have a backup of your database, you should probably reinstate that then just run the upgrade script over it before connecting your new store version to it