Picked up a Samsung Galaxy Player 4 a few weeks back, and have to say that it is flat out the slickest piece of electronics I have ever owned bar none.
In the past, I haven't been much of a fan of reading on one of these smaller smartphone style devices, but with the Galaxy Player 4 the screen quality is such a step up from all the devices I have seen in the past that it's a whole new ball game and I am really loving it.
The Samsung Galaxy Players offer most of the features of a cutting edge smart phone like the new Galaxy S2, Nexus, or Note models but minus blood sucking phone data plan. Ok, in fairness, compared to these other Samsung flagship models, there are also some other compromises like a somewhat lower end CPU and Lower Megapixels on the built in camera, but considering that my Galaxy Player 4 cost about a third what an unlocked high end smart phone does, I am not complaining.
In addition to several eReader apps like FBReader, and Coolreader, my Galaxy Player runs TONS of other Android apps like Google Sky, Google Maps, etc.
So it's not just a great eReader - it's a GREAT full featured Android tablet device.
Think about it; for less than what Amazon is asking for their own very basic Android based Kindle, which has no Cameras, Microphone, GPS, Compass, Bluetooth or MicroSD expansion slot, you can get a device that offers ALL those features (plus more) in a tiny ultra-lightweight pocket-sized package.
Of course the Kindles screen is larger, but it's also a lot bulker and heavier, so that's a trade off, and I already have a very nice Vizio 8 inch tablet with a GREAT 1024x768 screen that blows away the Kindles for reading full page PDFs so I wasn't too concerned about that.
So I decided to go with the Galaxy Player 4 as opposed to the 5 inch model and try for as many features as possible in as portable a package as possible.
I suggest you go to a local stocking retailer and audition the 4 inch and 5 inch screen models side by side and make up your own mind, but I don't really think you can go wrong with either.
Battery life is listed as being better on the Galaxy Player 5, so I wasn't sure how the Galaxy Player 4 would stack up, but by managing the power just a little I am getting really good battery life and can easily use the player all day (by setting reasonable screen brightness, and turning off wireless and sync when not needed)
For me, the deal clincher was the fact that the smaller Galaxy Player 4 has an easily swappable battery, and I was able to find a low cost source online for extra batteries
as well as a external charger
(note the above linked batteries and charger are listed for the Samsung Galaxy S Mini Phone, but also fit and work perfectly in the Galaxy Player 4)
Also, unlike many other Android devices that need to be fully shut down all the time to avoid sucking down the battery in 'sleep' mode, my Galaxy Player 4 uses almost no power when sleeping (which means you can just tap the power button to put it to sleep when not using it and INSTANTLY wake it up for use without waiting for a full bootup).