Nice pic there!!
I use my bikes alot, so tend to use any means necessary to transport them. I have been using roof bars from halfrauds for a while now, and have been using their carriers too and have no issues at all. The only things are that the locks aren't great, but then when I'm not with the car, I'm on the bike...
The only thing I would say is it depends on the weight of the bike also, I've used them for my bmx, trials bike and xc bike, but the heaviest being around 25lb(xc), but would not consider putting the downhill bike up there (some 42lb's!!) more so because its a long way to lift it up!!
It can be tricky sometimes as you have to line the wheels up to get the arm into position first, so you have a large cantilever where you are holding the bottom of the forks or chain stays whilst getting hitched up etc on your tod.
The ones I am using are the Halfords value roof bars and the halfords 2 roof carrier. I found the only difference with the value roof bars and the more expensive Halfords ones is the value ones do not have a lock!! The bars themselves will only take a certain amount of weight, so I tend to have the carriers toward the mount anyway, I doubt it would be worth running more than 2 bikes tbh. Naturally it is a case of how much do you want to spend, i haven's any others so would not know the differences really.
From a practical point of view, it keeps the bike outside and gives plenty of room in the car. Mud and grit however are not the most welcome things on the roof either. I'll try this link below where i have it strapped to the roof.
The roof mounts are great if you are all in the car fully loaded, but otherwise if I'm on my own or with friends I tend to get the bikes indoors!