I have the OEM Compartment separator and it seems fine to me. The only nitpick I have is that the hole for the middle seatbelt is way bigger than it needs to be, but it hasn't adversely effected me.
It was easy to install myself. The only tip I would give here is that it didn't seem like the little bumpers would slot into the indentations on the sides of the car, because my back seats were all the way reclined, pushing the top part of the apparatus backwards. When I noticed this I was really pissed off, thinking that with it installed I wouldn't be able to fully recline the back seats. But after inclining the seats and installing the whole thing, I was indeed able to recline fully.
It isn't as easy to set up and take down as I was hoping for, I wouldn't want to do it every week, but it's probably only a 10-15 minute process once you've been through it one time.
And it seems very secure, and it doesn't prevent the use of the side cargo nets if you have those, which is another thing I was worried about.