The first sign of malfunction was that the MBP started to be picky about what sort of blank CDs/DVDs it would accept for writing. This was not a big deal since it still accepted 9 out of 10 CDs without any problems.
Some time later I had a failed burning. The burn process started OK, but near the end (or maybe during writing the lead out?) it failed with some mysterious error message. This was quite strange, but I was still not very suspicious (this is my first Mac and having grown up using PCs with Windows I got used to failures).
However lately I started to have problems even reading my CDs and DVDs.

This was the last drop of water in the glass. Every sign pointed to either a broken optical drive or malfunction due to dusty lens. I already had issue with dust on the lens of various CD/DVD drives in the household (eg. the Hi-Fi system and my old PC had problems reading CDs too and a manual cleaning of the lens helped - I tried a lens cleaning kit too, but it was worth nothing).
So I was up and ready for cleaning the lens of the MacBook Pro's SuperDrive, however I was a bit unsure about whether there's any gotcha in taking the SuperDrive apart. I had no difficulties with my old PC's 5.25" Plextor DVD-writer (you just had to remove the screws from the drive's case and take off the upper part and the lens was right there), but I've never taken apart a slot-loading drive. Notebook optical drives are a lot smaller and I wanted to see some proof-of-concept photos to get reassurance. After having spent some time with Google, I've stumbled on a
discussion thread on Apple's forums that contained a few pics of a slot-loading SuperDrive's internals. It didn't seem risky to take apart so I started the process.
Note: some people had success with using a plastic card (eg. a credit card or a drivers license) and some fine cloth (eg. the ones that you used to clean your glasses with). Some applied alcohol too to improve the cleaning effect. This way you don't have to take apart the MBP, so might want to check out the comments and read through the experiences of others with the plastic card method before you start to dismantle your MBP.
The first step is to take apart the MacBook Pro.
iFixit has a very detailed guide on how to do this, so I'll skip over that. After you got the optical drive out from the MBP, you place it on your workpad like this:
As you can see, I've kept the tape on the ribbon cable. I didn't see any reason to remove it. If you've followed the iFixit guide til the end, you've already removed the mounting brackets from the drive. You should memorize which bracket goes to which side and which screw goes into which hole. Otherwise the reassembly will be a little tricky for you.

I've taken some pictures of the brackets, it seemed to be the fastest way to take a snapshot of the original mounting of the brackets.
After you've removed the brackets, you've to take off the four screws that keep the lower and the upper half of the unit's case together. Here's a pic with all the brackets and these 4 additional screws taken off:
Now you can remove the upper part of the case. It's really easy to do, just do it slowly, no need to hurry. You'll get to see something like this:
Here I've drawn a small red circle around the lens:
For cleaning the lens I use benzine (the one used for medical disinfection ... we used to have a bottle of this at home): it's great dissolvent (eg. to remove glue that remained on a newly bought product after having removed the price sticker) and it evaporates practically without a trace. It's perfect for this kind of a job (however I've read that some people prefer to use some kind of alcohol).
To apply the benzine to the lens surface I use q-tips (that should not be hard to get either

):
After the cleaning the lens is as good as new:
Reassembling the unit should a be a piece of cake. Put it back into the MBP, put the MBP together and test the optical drive's CD/DVD reading and writing capabilities to see if the cleaning had any positive effect. For me it was worth the trouble. I can now read every CD/DVD of mine again and writing works perfectly too.
Update (2010.04.04): it happened today for the first time -since I wrote this article- that I could not read a CD with my MBP's superdrive. The time period was almost 20 months. And since I bought my MBP during Christmas in 2006 (dec. 27 to be precise), it was 20 months between the date of purchase and the first cleaning. So it's now quite certain that my drive needs cleaning every 20 months. I leave near a road with a pretty high traffic and not too rich vegetation, so a lot of dust is coming into the flat. Probably people living in the suburbs are better off regarding the required cleaning frequency of their optical drives.
Comments
Or you can just insert a cotton swab in the slot...
The lens is right inside the slot on the left hand side. About an inch in. Easily reachable.
Just a thought.
-LT
Re: Or you can just insert a cotton swab in the slot...
Q-Tip won't fit but...
Re: Q-Tip won't fit but...
Combined free solution...
1) Don't use compressed air since it will just make things worse: it's going to blast all the dust inside...
2) Don't try to squeeze cotton swabs through the optical drive since it's too big and will leave some stuff...
3) Cleaning CDs may work but cheap ones may damage the lens by scratching it.
4) Quick free solution: I used a thin plastic (came with the packaging of an SD card, but you can get any plastic used for packaging goods - usually the ones for electronics are tiny enough and strong enough for the job) + iPhone cleaning cloth (other similar cleaning cloth that's thin and doesn't leave marks for example for cleaning glasses). I wrapped the cloth around the plastic (like U shape around the front of the plastic), then while holding the ends of the the cloth I inserted few centimeters from the front of the plastic covered with the cloth in the optical drive, pushed and pulled a bit and it was all cleaned. The drive works perfectly. Just a few tips: I placed the cloth a bit to the left since LT pointed the lens should be at the left hand side. Don't use too bulky plastic or cloth since you may damage something or get it stuck inside. Hold the loth so it doesn't get inside the slot. You don't need to insert it so much since the lens is not so deep inside. It's just few cm in. All took me exactly 10sec to do. NB> turn off your laptop while doing it
Hope this helps
Re: Combined free solution...
iPhone cloth + business card
This was by far the simplest and harmless solution given. My MBP superdrive is now reading and burning cd/dvd!
plastic card + iphone
Credit card and a cleaning cloth
Wow, this is GREAT!
Whatever the case, Thanks!!