Pros: Sound Quality, BBE EQ, Battery Life, Durability, Buttons, Usability, Drag&Drop, MicroSD Slot, Screen, Powerful and Clean HO (works well as a LO)
Background: When I lost my S9, I had to find a replacement. I began to look for options, noting the Cowon J3, Nationite S:flo2, and Hifiman HM-601 as possible options. Then I discounted the Hifiman for the sake of portability. I spent a long time deciding between the J3 and the S:flo2 and eventually went with the J3 for the battery life, usability, reliability, and the digital volume control, as I like to keep my player on volume level 1 and leave it there in order to preserve my hearing as a musician.
I just got home from a trip today and this pretty young thing was waiting for me on my desk. I loaded 30gb of FLAC and listened for an hour, then decided I had to post a review. In short, this is my new favorite mp3 player. The S9 was awesome, with a few flaws. The J3 fixes them.
The button placement is so much better. I can put the screen on lock, and put it in my pocket, not worrying about the tactile buttons being pressed on accident. This gives me control without having to fiddle around with unlocking the device.
The MicroSDHC slot is a godsend to those with large libraries or love to discover new music. With my S9, I always wanted more space. I love to transfer new albums I haven't listened to to my player and either delete or keep them, then repeat the process. With the S9, I had to keep deleting old albums that I liked somewhat in order to keep listening to new music. I have this card (http://www.amazon.com/SanDisk-32GB-microSDHC-Memory-Package/dp/B003WGJYCY/ref=sr_1_2?ie=UTF8&qid=1294027856&sr=8-2) coming in the mail and I look forward to having 64gb of FLAC music in my pocket at all times.
The speaker is alright for music, but surprisingly useful for movies and videos. Xvid videos from perfectly reputable sources (cough) look amazing on the AMOLED screen, and seeing them is the point where most ipod touch owners will acknowledge the validity of your purchase. But hearing them adds a whole new sense to the experience. Its actually a decent speaker, beating the tinnier apple speakers to my ears, and goes fairly loud. Great for showing your favorite movies or playing your favorite new track for your non-audiophile friends.
The UI is just slick. I love it. It's so much cooler than the apple products I have used, customizable with user-created themes (http://iaudiophile.net/forums/forumdisplay.php?f=111) and has easy access to the J3's capabilities directly from the music and video screens. Cowon really listened to feedback it seems. This UI is just a joy to use. The S:flo2 aint got nothin on this.
Extra battery life - more to love. I mean seriously, 64 hours battery life for music is almost overkill. But 11 hours video on the J3's amazing screen is perfect for long commutes and trips. And who wants to worry about charging their mp3 player all the time? I watch friends having to plug their ipods in halfway through the day and smile, knowing that I could listen to music for almost 3 days straight without stopping to plug in my J3.
In short, I'm loving this little miracle so much, and I'm sure it will get even better in time. It's said that Cowon players have a slight treble emphasis. I can clearly hear everything in my music with the J3 and Westone 3 earphones. So no worries about out-of-control treble - there may be a slight emphasis, but everything sounds great to me. Another note about this pairing is that the Westone 3's, which hissed slightly with my S9, have NO hiss whatsoever with the J3. I can't hear anything but the music. And it's reproduced so beautifully. With the EQ off, its just me and the music. But using BBE EQ effects, it becomes an infinitely customizable music experience, which is really nice when plugging into my friends' stereo systems.
Get one now and stop being indecisive. You know you want one.