Boardsource Lulu. Built with Gateron Silent Ink Black and MT3 Susuwatari.

It has been my most used daily board for the past year and a bit more. First split, first ortho, first custom build for me. Coming from a 75% board with traditional stagger there was some adjustment mainly due to the ortho nature (but otherwise I was already using IJKL as arrows on the 75% board for example). First couple of days I was typing at 9 WPM (down from my then usual 90-ish), I needed a week to get back up to around 70-80 (fortunately I was between jobs then, so it wasn't critical).

In terms of layout I think this is the perfect amount of thumb keys that's manageable for me (on the bottom left I have Super/Win, Alt, MO(1) and Space, and Ctrl is to the left of A). I have another board with more keys there and they're not all that useful. I think however that I could do with a few more keys in the inner columns - on this board in particular if I want to use rotary encoders, I have to sacrifice the keys in the inner column, and those keys are useful for brackets and also for some primary letters in my native language (Bulgarian - it has 30 letters in the alphabet). I've tried home row mods, but I don't think I can rely on those as the sole way to access a mod. I personally couldn't do without the number row even though I have a num block on a layer - so 60-ish percent is fine for me for most things.

I'm pretty happy with the build quality. One thing I don't like is the plastic bottom - if you don't tighten it properly it rattles a bit, and every time I go about tightening it I'm afraid I might crack it.

I really like the MT3 profile keycaps - they basically hug your fingers in such a way that it's pretty hard to get lost on the layout, and it also encourages proper ten finger technique. As for the switches - I get why people generally recommend lighter ones for split boards - I find those a tad too heavy. Also in stock form they're not fully quiet and have some mush to them (I guess it's inherent to this kind of silent MX switch). I might do a spring swap and lube at some point, or maybe swap the switches entirely (since I have another board that I lug to the office, this one doesn't really need to be quiet any more).

Another board that I'm looking forward to is the ai03 Altair - it solves most of my gripes with the Lulu in that the case is fully aluminium and that the layout has a few more keys in the inner columns. As an added bonus the halves connect using USB-C, not TRRS. The only thing I don't really like is that it has neither a display nor indicator LEDs - so managing multiple layers would be a bit harder unless I find a way to add a LED somewhere. I have the Dark Grey on preorder and I'm probably putting MTNU Graphite keycaps (or perhaps something like MT3 Darkness) on it.