Pros: Very well balanced and very precise sound, no major flaws, adjustable nozzle angle
Cons: Slightly springy cable, over-the-ear only, sibilant/presence boosted with certain tips, slightly warm, could have more highest end
VSonic GR07 is a great example of IEM strong because it has few flaws and almost all of these are possible to correct with a good equalizer.
Bass is perfectly controlled, excellent texture, very well extended (-6 dB at 30 Hz with perfect seal), perhaps a bit warm due to high-bass boost (~250 Hz). No bass bleed is present.
Mids can be slightly forward to slightly laid back depending on tips and depth of fit.
Highs... here's the issue. With shallow insertion, there can be a fair amount of lower highs boost, around 6kHz, which combined with some highest end peaks can sound sibilant. Using foam tips helps with this, deep insertion completely removes this issue. GR07 don't have a lot of energy at the highest end, but they do have extension, so it can be corrected.
Timbre is excellent - delicate and unassuming, with excellent detailing, not overly aggresive and not overly smooth.
Soundstaging depends on depth of fit. With shallow fit, the soundstage isn't the widest, but is quite competent - with minor positioning issues due to sibilance and high-bass boost. With deep fit it is perfect, both width and depth, there's vertical resolution too - it will unfortunately make all recording and mixing flaws in this regard obvious.
Fit is excellent both for deep and shallow insertion due to rounded edges and no molding artifacts, small enough size and adjustable nozzle angle as well as a fairly large tip selection. GR07's nozzle is unusual sized though which limits possibilities. For Comply foams, T140 is the correct size.
Isolation is good for dynamic driver IEMs, microphonics are nonexistent.
Cable doesn't tolerate any kind of rotation around the axis of the cable for the part above Y split. If any is present, the cable tends to jump off the ear. This is easily remedied with the included ear guides or neck cable adjuster.
3.5mm L-shaped jack is iPhone friendly and seems very sturdy.
Build quality is very good with a minor exception - the strain reliefs tend to come apart from the body of the IEM. Easy to fix with a dot or two of superglue.
GR07 are efficient enough to be driven directly from a portable, do not gain a lot of quality when amplified.
Their main problem is availability - there are few sellers and those can be a bit remote.
Now that my RE272 cable broke, I'm stuck with these. They need somewhat extreme equalization to get rid of the presence boost, but with T200 Small, truly a winner.
Of course they're somewhat less analytical, slightly lowpassed (17.5kHz) but beautiful texture.
Without eq they are pretty harsh and "flat" sounding, as in no depth, likely due to presence boost.
Equalization lets them have great depth resolution too.
GR07 bass sure is fast and tight, but it has less natural decay than RE272's. Kind of like it's trimmed or slightly compressed. However, vocals are presented far more liquid and with better detailing, while higher end (presence) sounds a bit electric/harsh even after correction.