It works perfect with wp 3.9 and wp 4.1

This plugin it is fantastic and be careful with the bad reviews because some can come from paid plugins owners…

There are some things to have in mind if you are importing lots of post like in my case 100.000.

If you have your site in a shared host I would recommend to do it local and then upload the db to the production server so you can increase the php variables:
memory_limit =128M
post_max_size = 64M
upload_max_filesize = 64M

Also will be better to do chunks of 20000 items.

If you are getting duplicates categories the typical cat_1 cat_2 etc thing it is probably because you have some rubbish in the terms table that are not showing in the category or taxonomy you are using.

you maybe also have to update the count of the taxonomy table

Thanks for the plugin,

Eduardo