I have 2 e-readers (Nook & Kindle3) but not because I got tired of reading with just one reader. I prefer the Nook because of the swipe page turn & touch keyboard, but like the Kindle because of the weight & battery. The reason I got the Kindle is because for quite some time B&N wasn't providing nor giving deals on the type of books I wanted to read. That's changed now.
I do enjoy reading on two different readers though.