I've been testing the p0 Hybrid for my uses with tabletop and light duty field uses.
On my light Manfrotto CF090 series legs, I find it does a fine job even with the big SL90-280 lens for the tabletop work: There's very little residual vibration when tapping the tripod, focus and exposure are easy. Outdoors, there's a bit of motion in light wind that I can damp down with a camera bag's weight and I'd say the use is "acceptable" if not brilliant.
On my larger Feisol CT3442 legs, fitted with the center column but not extended, performance is excellent for both indoor and outdoor shooting. Of course, when I switch out the column for the flat plate, it gets even better. Light wind doesn't bother the setup at all; add a bit of weight if the wind goes to 'heavy' and it stays good.
Overall, just the head alone:
The detents in the geared adjustment I don't find troublesome. They are there but they don't hurt positioning precision or stability that I can tell. The much heavier detents in the panning adjustment are a bit more of a nuisance: making fine adjustments when you get into the range of the detent is more difficult than it should be. It wouldn't be so annoying if the detent was about a third the strength. They make smooth, dynamic panorama captures with something like the iPhone impossible, however.
I'm waiting to hear further from Rod about a modification that will remove or greatly lessen the strength of the panning detents.
Comparing the level adjustment with the SL's built-in viewfinder level ... The head's bubble level is well within the built-in level's range. When I turn the adjustments, the built-in level's plus/minus point is about 1.8°, evenly in the middle of the adjustment range. So this works well, up to its resolution. I find using a two-tube bubble level, or a large circular bubble level, mounted in the camera's accessory shoe is the more accurate, higher resolution way to ensure a perfect level however. The goniometer adjustments make it very easy to set a perfectly level camera position this way.
For use with the SL24-90 and my remaining R lenses, I'll want to use either my general purpose L-bracket or a dedicated L-mount camera plate for the SL. The latter is much more convenient
I also tested the head briefly with my Hasselblad SWC and 500CM too (using film). Given the range of lenses I have (38 to 150 mm), it worked very nicely. I can't imagine that it has any negatives for use with this camera system, presuming I use the mirror lockup on the 500CM as I normally do for longer exposures.
The QuickLink head mount is quick, secure, and handy. It adds another small bit of height to the top of the tripod column (estimating about 10mm) and about 3 ounces more to the weight of the tripod head setup.
Overall, I'm happy with the p0 Hybrid and QuickLink head mounting system for my purposes. I think it will be improved with the lighter/no detents modification on the panorama movement, even if that does slow down setup and use a bit.
G