I love the Galaxy Tabs. They are not a replacement for laptop or desktop as there are many things they won't do.
Galaxy Tabs has Polaris which is a decent substitute for MS Office. With an external keyboard the office style environment can work well but is very limited.
The Zagg keyboards can be nice, but I have had problems with mine and due their price I am just not interested in getting another one unless they can prove it is problem free.
Best things about the Tabs are that they make a great Kindle reader. They work well as an Internet web browser and running some decent apps. If you have videos you can download, then they are pretty good as an entertainment center.
Where we use ours a lot is travel. If you install weather apps they make a great radar. It is hard to beat as a navigator since you have a huge screen for Google Maps.
The other thing that is useful is using YP to find the best fuel prices. I wish I could set YP to follow the Google Map route and find those cheap stations for me, but it is still quite nice.
Once I find candidate stations I can route through Google Maps and then use street view to check out the gas station approaches for RV friendliness. Cannot beat that with a stick in my opinion.
They also are great as a photo album when you want to bore people and the newer ones make for a decent camera. They are great for Skype too.
Generally if you upgrade your phone and buy the tablet, you can get phone and tablet for less than the cost of a tablet.
Biggest problem is battery life. Most do not seem to charge fully while you are using GPS and they tend to overheat and need some time to cool down and recharge. That takes most of the day to do so it is really just a nuisance.