They are quite easy to assemble, once you get through the first one which will probably seem complicated until you do it and understand all the connectors and such. Well within the grasp of anyone who can read instructions.
Just be aware that these are particle board components and will not stand a lot of abuse.
I've used them in the past but just did some custom updates that are so much better. My wife wishes I'd done it long ago. After deciding the width of my hanging areas it wasn't too difficult to cut and install the boards. The best thing we did was to order closet rods and fixtures from www.closetbay.com. This stuff is so strong I'll never have to worry about it bending or falling down, it's high quality stuff like you'd see at a store. (My wife has a lot of clothes and they are quite heavy!) I can also install more shelves easily if I want too so there is a degree of changeability if we need. I made it in pine and painted it but for more money a really nice closet could be done with cedar. This is a major improvement over the wire shelves!