Sometimes, we need to import Sitecore content data in the scope of migration or deploying process. In general, we can use Sitecore Migrations tools (if we need full migration). But if we just need to export content data, we can use Sitecore Package Designer, Unicorn or TDS.
In my case, we needed to migrate dozens of content items (more than 40 000) from Sitecore 7.5 to Sitecore 8.2. And we had only Sitecore Package Designer.
The main issue we faced was the long processing time (a couple of hours) of Sitecore Package Designer. This was the trigger for us to release our Sitecore Data Transfer tool.