VNAV on the 777 is somewhat flawed, IMHO. That doesn’t mean you can’t get it to do what you want but you have to be aware of quite a few issues. Our FCOM has many pages devoted to all kinds of VNAV anomalies.
One of the peeves I have with VNAV is that it is sometimes not very good at telling you in advance what it’s going to do - whether it will fly level, follow a particular path or start an idle descent is not susceptible to prediction in some cases. There are un-annunciated modes which have a big effect on system behaviour. This means it is sometimes a bit difficult to say whether it is behaving oddly because of finger trouble or because it has chosen a different way of doing things *today*.
The seats are crap but it doesn’t help that no-one except me seems to snag worn out cushions in the AML. A decent car seat would be much more comfortable on a long flight but I suppose it forces me to get up and walk around fairly often, which is a good thing. My glider, which has a thin layer of crash foam over bare carbon, is peachy for an 11hr+ flight and there is very little room for manoeuvre in there!