Sooo... Where to begin this update... Yes, I'm still alive, and I finished the project not long after the last update. The system has been running for 3 years now, and it still works like a charm.
My wife wanted to know why I wanted to do this, but soon after the kitchen was ready, she told me that it was really something that she never knew she needed, until we had it. So I consider the whole endeavour a great success.

Things learned: it's proven to be very helpful to stick the double-sided tape to the aluminium srips and the LED strips and let them rest for a while so the glue can bond, before you put stress on the tape by hanging them upside down. The only strips that came off, were some of the strips which were directly stuck onto the underside of the countertop. You can use Polymax or JB Weld for those.
It's also not necessary to get yourself a power supply which can supply power to ever strip at the same time. The ANSLUTA PSU's were cheap (because of them going out of IKEA's programme, to be replaced by a dimmable version), but in the end a bit overkill. The positive side about that is that I don't have to worry about maxing the thing out EVER, and I'm confident that this supply will last longer than the kitchen itself.

Abviously, you don't HAVE to use IKEA supplies: any old 24v power brick will do, as long as you don't draw more power than the PSU can handle. The upside of the IKEA ones is that they are made with safety in mind, and can be connected in a very simple way, which is key if you want to build something that should be able to outlast your use of the product.

The LEDBERG strips are a bit chunky though. If I were to do this again, I'd source some decent LED strip with a good bit of double-sided tape, and make it all a bit more flat than the current strips already are. The OMLOPP lights are thicker, and while I understand why, I do think that IKEA may want to re-design the OMLOPP lights.

You see, there were a number of reasons I started this project. The cost was a big factor. Even now, with LED lighting cheaper than ever, the OMLOPP lights are still quite expensive, and when you take everything but time into account, my LEDBERG hack has cost me about one third of what OMLOPP would have cost me: 26 lights and 4-5 power supplies still set you back about €900.
Another factor is the amount of light coming off OMLOPP. Comparing the two, OMLOPP is definitely brighter than LEDBERG. However, LEDBERG's LED-chips are more evenly distributed, as where OMLOPP has 3 LED-chips grouped in one spot.
The 80cm version has four groups, the 60 and 40cm only have two. Not really a problem when you want to light up a large drawer, but a utensils-drawer is quite dark in the lanes which don't happen to have such a cluster.

So it would be good if IKEA would re-design the OMLOPP lights, to have more LEDs evenly distributed, and a lot more flat than what it is now. The magnets are a great help when fitting OMLOPP, but after that, they are useless. If they would leave those out, or put some smaller ones in, for instance...

Another tip I would like to give you: get enough LEDBERG to last you a while. One of the strips went missing, for some reason (glitch in the matrix, probably), and I used up my 24v LEDBERG stash on other projects, so I went and got a new set. They added some notches to the strips, and the thickness of the connector is different, meaning that the new strips fit the old connectors, but not the other way around. So in this case, it turned out fine, but if IKEA re-designs them again, one may not be so lucky.

So in the end, this labour of love has served us well, and we expect it to keep serving us well for years to come. I might replace the system at some point, but by making the power supply available behind each drawer, I'm flexible enough to switch to optical sensors if I feel it to be necessary. The switches are holding on, though, so I don't think that'll happen soon.