I think I've had these long enough now to post at least semi coherent impressions, though by way of a disclaimer I did buy these for the looks as well - kitsch is cool in my book.
First thing to get out of the way is that even though there are sets that I do find fatiguing because of their mid bass emphasis, GK10s are not one of those sets, though the wrong tips will definitely make them sound terrible - in my case it was XL CP100s - with instant mid bass woollyness and general dullness across the rest of the range. I moved on pretty quick.
Notwithstanding I might have a completely different tuning to anyone else, it's definitely worth tip rolling with these - the 2 configurations I've really liked so far have been: narrow and short bore Sony hybrid clones (similar to the stock narrow bores but softer, they make for a more secure fit), which give a nice balanced tuning akin to something like a more detailed Final E1000, very relaxing but at the cost of some detail as there's a little bit of haze over the mids and treble, and: using a horn shaped tip (Flare Everyday Earfoams, in my case, which aren't actually made of foam but are one of the relatively few tips that fit me) for a boost to upper mids and treble - more of a KBear Believe kind of tuning, though with different technical characteristics (much more separation but thinner and brighter tonality) very clear and dynamic and just the right side of my midrange sensitivity (so a little more reserved than the Oxygens of this world - and the Geeks are definitely in the same overall ballpark, even if they present themselves quite differently, especially tonally). I'm aware this isn't everyone's experience, hopefully it's not unit variance and there's a tip option out there that snaps them into focus for you - I was surprised at how big a difference tips make on these, especially to the bass clarity, and very glad I found something that worked for me.
Onto the staging and imaging, this is where I have to agree with everyone else who swore GK10s were awesome. They are indeed very good, very evenly weighted (as opposed to centre weighted, if you will) and wrap around, and I'm seriously impressed with this aspect of the sound, the resulting imaging is all very coherent and clear.
One random comparison - I really wish my Dunu DK2001s were tuned more like the Geeks (less aggressive mids), they stage similarly but I think the 2001s have the edge on note weight and bass technicalities, with the Geeks winning on treble performance once I EQ the Dunus (mids are pretty much a wash, I think stage width is a bit better on Dunu after EQ). Without EQ I'd just listen to the Geeks.
Albums I've been testing with, Geeks definitely have versatility (using horn tips at about 90db, and balanced out from a Radsone es100, which has a 0.5 output impedance fwiw):
Tom Waits - Rain Dogs
Male Vocals: Old gravel guts himself, tonality sounds pretty damn good, vocals float front and centre without any issues, percussion has great weight and punch.
Strauss - Four Last Songs
Female Vocals: This is great as well, maybe a tiny bit of occasional glare/lack of transparency in the upper mids but that's compared to listening with speakers. Excellent details from the orchestra on this.
Stravinsky - The Rite of Spring
Separation / Layering / Imaging / Dynamics: Just great, feels like you're on the stage. Smooth and detailed, has no trouble managing hits (fun fact, the first synthesised orchestra hit was based on an unlicensed sample from Stravinsky's Firebird). Tonality seems fine, though I'm far from a purist about these things.
Santana - Caravanserai
Speed Test: Can the drivers keep up, especially with the treble percussion? Yes, piezos love this album, even when there's a blizzard of noises to process, and GK10 is no exception. Treble is really well controlled, and pulls out a lot of detail and inflexion from the mix. Also good with the imaging on this album, there are a lot of panning guitar solos going off, all really nicely presented with a very natural attack to the midrange with a tiny bit of diffusion to things like tomtom rolls (could actually be the recording). That said this is the first time I feel like there's anything really missing - I think the Geeks could use a tiny bit more texture and focus in the bass. I'm being picky but if there's one issue with their tuning of bass it's not bleed into the mids but the rolloff on the sub bass, which just needs a small raise, not too much or it'll kill the agility, but something.
Last one
Vangelis - Blade Runner
Immersion / Atmosphere: So many versions of this soundtrack, the Esper Retirement Edition is my favourite as a complete piece of music but this one has insanely good mastering and is a 100% chronologically accurate mix of the Final Cut soundtrack, with zero dialogue and character effects but all the ambience and music. Very cool and really lets you appreciate what a huge space the Geeks can render and how nuanced (and hard, very occasionally, but it's how the mix is mastered) the piezos can be. Lack of subbass should be a problem but really isn't - I'm too distracted by the sheer vastness of the soundstage and all the details that the dialogue was covering up.
TL;DR these kind of confounded my expectations, which were up and down like a yo-yo before they arrived. They're definitely impressive for the price IF you win the QC lottery AND achieve some kind of synergy with source and tips, at least based on what I've been reading and have experienced, but they do sacrifice note weight to achieve all that clarity. Would have loved it if the upper treble was slightly more diffuse and the sub bass a little more extended, but definitely glad I took a punt, they've really worked with some of my favourite tunes, so I have to consider my time with them as well spent.