I've had this thing for more than five years. It's awesome and I've recorded tons of stuff with it, recently a LP for my band, SHOOM, was all recorded on that white marvel. Check it at www.shoom.band
R16 is very useful, full of features and well designed. However, the thing that you should know is that ZOOM is a cheap brand and R16 is a fragile plastic box with low quality parts. Mine already has most of its input jacks not working with XLR cables, the gain knobs inject crackle noises etc.
The other major design limitations are 1. it records in 16bit format, no way to get 24 or higher. Some sound engineers cringe over that. 2. phantom power on two channels only 3. effects available only on channel 1
Still there's no other product on the market that does what R16 does for $300, so I do recommend it.
This is a great piece of hardware for someone who's starting out. 16 tracks of audio, 8 in real time, built in effects and sends, built in stereo microphone (!), audio interface capabilities (8 mono/4 stereo channels!) at up to 96 kHz, memory card slot for saving recorded things, you can daisy-chain the units to get more channels, and everything I just mentioned is battery powered. BUT! The build quality is poor, my jacks got stuck in the combi ports (I have to unsolder them from the mainboard), I have constant problems with it in audio interface mode (it's main purpose in my studio)...
So only get it if you need a lot of aforementioned tools in one cheap package. I did need them, but as my studio grew I now need something more robust anyway.
I read a load of reviews before I bought this and it does so much so well. I tend you use it as and interface and control service which is does well. I've read that recording on it rather than through it is also very good.