Apple’s iPad tablet is still very much dominating the market, but contenders from just about every direction — mostly on Google’s Android platform — are making a few tiny dents in the juggernaut’s armor.

According to a Nielsen study reported by Fortune, the iPad makes up about 82 percent of the current tab market, which is slightly down from the former heights the iPad occupied. It’s still really, really high, however, considering competitors from Research In Motion, Samsung, Motorola and numerous others.

Back in March when Apple released the iPad 2, CEO Steve Jobs touted that the iPad held a greater than 90 percent share of the tab market. Most talk around the Internet makes that figure sound at least mostly accurate — it may perhaps be fair to say Apple shipped 90 percent of available tablets, rather than sold 90 percent.

Nielsen’s results focus on “tablet ownership,” according to its report, and find that of U.S. tablet owners, 82 percent own an iPad, while the Samsung Galaxy Tab had 4 percent of ownership, the Dell Streak came in with 3 percent and Motorola’s Xoom commanded 2 percent. Nine percent of owners identified their tablet as being other than the three mentioned above.

Still, that means that there has been something of a decrease in iPad ownership in the last few months as the tablet race has heated up and seen the addition of the Xoom and RIM’s BlackBerry PlayBook. Samsung is even returning with new models of its Galaxy tabs meant to take on the iPad directly by making them thinner than Jobs and Co.’s newest creation. The champ has a target on its back.

Nielsen’s April survey also found some other interesting reasons why electronics companies are taking the tablet industry so seriously — tabs are eclipsing or even replacing traditional computing devices. Some of the most notable numbers: 35 percent of tablet owners who also have a desktop computer say they use their desktop less, or not at all; with laptop owners, the “less or not at all” crowd is 32 percent.

A few other quick hits from Fortune’s story:

  • 27 percent of those who also own eReaders said they use their eReader less often or not at all.
  • 27 percent who also own portable media players use their media players less often or not at all.
  • 25 percent of tablet owners who own portable games consoles are using those devices less often, if at all, since purchasing a tablet.

    The full summary of Nielsen’s findings can be found here on their blog.