Construction is of smooth hardwood with a nicely laquered surface, giving a solid high-quality feel - it seems very unlikely produce splinters when small teeth gnaw on it. Components fit together well and joints are linked using bolts tightened with (supplied) allen-keys, so the occupant has no chance of dismantling it. Assembly of the full octagon took (by a single person) about 30 minutes on the first try.
Each junction can be set at one of 4 pre-determined angles, ranging from 90 (square) to 135-degrees (octagon). Reconfiguring to a different shape requires undoing/redoing 2 bolts per corner so isn't trivial, but the upside of this is that once assembled the playpen is very stable and the joints don't wobble or flex. The door mechanism is simple for an adult to operate - it requires simultaneously squeezing a handle and lifting the door, so should be satisfactorily difficult for someone with small hands under 70cm tall.
In addition to regular shapes it is also possible to build a 'flattened' hexagon with 2 (opposite) 90-degree corners and 4 135-degree corners. One section is also supplied with the ability to form any angle between 90 and 135 degrees, presumably to allow construction of a barrier between walls rather than a standalone pen (we haven't tested it in this mode, though 2 wall-connection ends were included with the package).
Before buying the 7+1 configuration I'd recommend getting some bits of string and laying out the proposed area on the floor to determine if such a large size works for you, or whether you'd be better buying the 5+1 (or other) configuration.
The only change I'd make to it would be to have thicker wood throughout - not that I suspect it's inadequate as-is, just that I like things to be thoroughly over-engineered.