My experience coming from Ikea Marcus
183cm (6 foot), ~85kg
I've been using the same Ikea marcus for the last 8 years, it squeaks like crazy and the seat is completely hard but other than that it's been really good run.
I read a lot of libernovo reviews before I bought it and saw all the complaints about the seat depth. Good news for marcus users: the seat depth is the same as the marcus. If you're fine with the marcus, the seat depth won't be an issue.
There was an issue with off-gassing when I first unwrapped the libernovo, it made me sick just being in the same room as it for a week. Luckily it's temporary and I'm happily using the libernovo now for a couple months. (This is unrelated to marcus, but I haven't seen anybody complain about this before - it was a surprise and made me super sick as I didn't have anywhere else to put the chair)
The chair is very comfortable, the back feels like it's molded to me. The seat is softer than the marcus. It's not really fair comparing the 8 year old marcus to the new libernovo, but from what I remember, the marcus seat was never really that soft.
The libernovo can lean back way further than the marcus, so that's great, I've been using that a lot. However I do get sore after sitting in it all day. I can work around it by getting up more often, stretching, changing positions, etc. But I never had this problem with the marcus.
Happy to answer any questions. I still have the marcus for direct comparisons.