There is a good article on inattentive ADHD at Wikipedia under the title of "Sluggish cognitive tempo". The author of the article states that a number of researchers think that inattentive ADHD should be seen as separate disorder to ADHD, and that SCP might be a more accurate label.
There is a good link at the bottom of the article to a paper by Adele Diamond, which goes into some detail about scientific research into inattentive ADHD. Diamond believes that the primary cognitive deficit in inattentive ADHD is in "working memory", which accounts for the mental sluggishness experienced with this disorder.
Living with inattentive ADHD is a bit like surfing the web on a dial-up connection, while the rest of the world is on wireless broadband.
If inattentive ADHD were labelled as a separate disorder, then it would help attract some overdue public interest in this often overlooked condition.
In the mental health field there always seems to a lot of initial interet when a disorder is newly defined as has been seen with bipolar disorder, ADHD and Austism. However, since inattentive ADHD is currently submerged under the wider ADHD label, it hasn't had a chance to receive that initail public exposure.
A lot of people are also spectical of the ADHD label because it seems to cover a number of different conditions and hence perceive it to be a catchall disorder with little scienctific basis. If inattentive ADHD was labelled separately, then this would allow for a more precise definition of impusive/hyperactive ADHD.