The R-4 arrived late last year. I wrote comments on it then that
included:
1) Very portable 4 track recorder
2) Mic preamps with marginal gain--often record will levels at max.
3) 10s of hours recording uncompressed 44.1/16 using the internal drive.
3) Batteries do not engage when power drops--only when AC is
disconnected.

After several sessions I can give more insight.

Mic preamps are "OK". While the mic preamps are skimpy on levels, the
results are about average for what I consider pro gear, i.e. a little
better than my Mackie SDR 24/96, but not as good as my Cranesong Spider.
Noise levels are low. Fidelity is good. Even with (euphemistically)
lots of headroom raising the levels to peak at -1 dBFS doesn't cause any
noticeable problems.

Note that there are no separate line inputs and no mic/line switch. The
same preamps handle all levels up to +4.

Remember the old piano key cassette recorders so popular in the 70's?
This machine has that capability. With battery power and builtin mics
and speakers, I set it on the floor at a rehearsal and recorded the whole
thing. (I practice to the rehearsal recording).

The R-4 is not noticably better than a $10 Radio Shack cassette when
using its internal mics and speakers (except that it's stereo). The
builtin omni mics don't suffer from machine noise, at the R-4 has no
moving parts, but they aren't better than my mother's old cassette
recorder. The speakers remind me most of a cell phone, tinny and zero
fidelity. They are marginally better than the meters for verifying
input. It had no trouble running for the 2.5 hour rehearsal on NiMH's.

The meters. They read from -48 and have a clipping indicator. I find
them useful. Now that I'm used to the display, I find I can read and
change it easily.

I'm now addicted to the "preroll". The recorder keeps the previous X
seconds (default = 14 up to 60) in a buffer. When you hit record, your
recording starts 14 seconds ago. I can wait for the concert to start and
hit record after the fact. Saves many minutes of dead air when I'm set
up offstage and out of view.

Overall, I find it a good, middle of the line recorder. It's definitely
a step up from the DA-P1 DAT recorder it replaces, and I find many
sessions (I record mostly live, classical programs) need only the 4
channels, saving me from having to truck the big rig. The R-4, two
stands, 2 stereo snakes, 4 mics, headphones, and a UPS are the whole
show.