Well, on that note, then I'd like to share a little 'bug' I came across if you choose to use Excel to edit/create easy populate files:

If you have sku numbers that go something like: 0021

Then remember to have Excel save the sku number column as a 4 digit numeral, or it will save it as '21' and it will just create new products, in essence a copy of 0021 if a product with the sku number of 0021 is already in the database.