I have been a heavy user of GeoHex since it came out. Both Green and Desert with at least one of every add on set that came out plus custom pieces the owner made. I find it the most versatile terrain system to cover almost any terrain situation needed.
I have a 12'x6' table designed to hold GeoHex so it stays in place with no issues. I start with covering the table with brown cellophane for any water and build up from there. If there is no water then I roll out my green or desert mat to cover the table and build up from there.
I never use the connectors. If the pieces are resting on the mat, they won't slide around. If its on the cellophane it may slide a little but the weight of the other terrain or figures on top usually is enough to hold it in place.
It can be a bit of a challenge at first or if you don't use it that often. If you don't have the "half pieces" to match up at the edges of your table it can be tough to get the shapes you want. I've been using it for so long I can set up a complicated table quite quickly.
Storage can be a challenge. There is just no good space saving way to store GeoHex that I have come across. I have a number of large Sterilite containers that work quite well and a dedicated storage area just for the GeoHex.
It can be fragile but in the 30 years or so I've had many of my pieces I have never broken off a corner. Maybe I'm more careful than most in handling it. If you do get a chip its easy to repair. I use thinned Durhams to fill in because it dries rock hard and takes paint and glue well.