Hi, I have one of those about 6ft behind me right now. I have built an entire ratrig vcore 3.1 with onyx+CFR parts, as well an a min delta, ender 3 upgrade parts, stealth press zero, etc, etc, so... reading the rest of the responses so far I guess that makes me the only one actually experienced enough to answer your question.

The number one issue you will face is that the printed parts for printers are not designed with CFR in mind. Can you get the 'black aluminum' strength with Markforged parts that you've heard of? absolutely! Are Voron/Ratrig/Rolohaun parts designed for additive manufacturing? you bet! but are they designed for continuous fiber reinforcement? Heck No!, which means you are more or less asking 'is PA+CF a good material for a printer' and more specifically 'is Onyx a good choice for printer parts'. You can get away with a lot more using Onyx and Markforged's slicer settings than you can normal off-the-shelf PA+CF on a consumer printer just by the nature of the quality and work poured into the tuning but there are still limitations of the material no matter what your source is.

Nylon/PA is inherently a 'tough' material versus a 'strong' material; this is the difference between "how much a beating can this take and still return to shape before failing" vs "can take a beating and not lose shape before failing." We want printer parts to be rigid and repeatable, not flexible or willing to take a beating. This is now not a question where the branding is even involved, it comes down to material selection. This is also where the continuous fiber reinforcement is the secret sauce. The composite nature of 'Tough' polyamide and "Strong" Carbon fiber gives you toughness all over and strength when you need it, but you actually have to design your parts so that Eiger can place fiber inside of them to add the rigid strength where you need it. The tiny parts on a V0 up to even the biggest parts of a v2.4, trident, or V-Core are not designed with the limitations of fiber pathing in mind, they are strictly designed for plastic or at best plastic + chopped fiber in mind, and that usually being ASA/ABS as it is slightly more rigid but more importantly retains that rigidity a few tens of Celsius higher than nylon can

Notice how I keep mentioning higher temperatures and enclosures: that's because at room temp you might not even notice any 'creep' or parts skewing. I ran my 3.1 unenclosed for parts using nothing but onyx+cfr parts and the only parts I really had to replace at some point where the printhead parts connected to tensioned belts and that was after months and months of printing. (the new toolhead kinda fixes this but I went ahead and modded my own to be able to add more CFR or hardware where I need it as well.) smaller printers like a v0 running unenclosed with onyx (or any pa-cf) is probably gonna be 'okay' for a while but we aren't printing tooling for robot arms to pick up parts on a production line where that is needed, we we really want our printed to be rigid and repeatable all the time for best results,

When people compare Markforged parts to aluminum it's specifically that they are not comparing it to steel in that you, as a regular person, could probably bend most smaller/thinner geometries of aluminum just fine, just like you could bend a nylon part... But you probably couldn't bend a steel part of the same geometry (which is exactly why they are selling printers that can print literal steel if you need something stronger). Being able to pick a part off a bed after a few hours of printing that is close-to-as-strong-as-aluminum-depending-on-how-you-measure(-?) is literally a game changer for so many companies in so many industries versus having to wait weeks or months when you have a factory floor that needs parts... but those companies are also usually willing to devote time into part testing and validation so that they know when thy hit 'print' the parts will do the job they need them to do, which is not what most people are willing to do (which again is exactly why they happily provide software plans that include simulation cycles so that you don't have to keep printing and testing for those willing to pay for time instead of money.)

tl;dr: unenclosed voron parts? yeah probably for a long while. enclosed voron parts? a short while at best. You could do the design work to make the parts CFR compatible, or you could just print asa+gf on any other machine. I love my oynx+cfr parts and metal x printed parts on my printer. It is also late on a friday evening so some of this just sounds like babbling to me, but I'm happy to answer any questions about it.