Here are my experiences during import/export of products.
While exporting products, if I encounter an error, it did not remember any of the checkboxes, so I have to check everything I want over again. It would be nice if it remembered from the previous screen. Even nicer if it remembered next time I wanted to export products. It is so nice that importing now remembers the previous import settings.
I like how the exported data is saved (pack) for later retrieval.
I tried importing products exported from 4.0. After waiting a while it finally comes back with "The path you have specified is wrong or you have not access to write to the specified path." It is now set to Server for source and shows "/u/svowl/public_html/eshop_main/files/import.csv" for the path. But I specified a file to upload from my computer. My import files was >2G which I know is bad and is the cause for the failure. Maybe a different error would be good.
After importing a smaller file, there was no message that anything was successfully or unsuccessfully imported. It just took me back to the import/export data screen. The last import log had no import information. This appears to be caused by not specifying [PRODUCT] on the first line and properly formatting the column headings. Maybe an error saying such would be good.
I like the use of "var" to hold cache, tmp, and logs. The named log files and log rolling is very nice. So are the Logging Options. While these are nice, nothing was logged that indicates why this was not working. I even turned on all the logging options.
It didn't allow an import from 4.0 export data since it had the Distribution, Product_Type, and Product_Options columns. It would be nice if it just disregarded columns that don't exist in the new products table. Or if it was optional.
I'd also like to be able to import product data from 4.0 to 4.1 without being required for it to be part of the cart upgrade. It seems the data format is not backwards compatable. This would not be good. Maybe an additional tool that does just this?
During import, it didn't like my native Excel .csv which has ^M instead of real line breaks. It would be nice if the cart could deal with this on import.