We first saw this with the Samsung N150 Plus (Samsung N150-11), which gains a larger 250GB hard drive (rather than 160GB), along with a special sleep technology which reduces its power consumption when in standby mode, a fast boot software, and a bundled version of Microsoft Office Starter Edition 2010.
They have now rolled out the Plus range to two more models from their netbook range. This adds the Samsung N220 Plus (Samsung N220-11), and the Samsung NB Plus (NB30-11B) to the market. Both feature the same larger 250GB hard drive, and we assume the other new features found in the N150 Plus.
Currently all of these Plus models seem to the U.S only. It is also interesting to note that the standard N210 / N220 in Europe original came with a 250GB hard drive as standard.
Also, in related news, the new Samsung N230 netbook can now be ordered for about $400!