I agree with your friend that if you use please in addition to another "softening" phrase in your request that it could be perceived as somewhat obsequious or even a bit sarcastic. 

As Adam mentioned, inflection is very important. These examples could be spoken in a way that makes them more of a demand than a polite request.  


  Could you possibly roll down the car window please? The next time you decide to eat 5 bean burritos for lunch, you should drive by yourself back to the office. 
  
  Would you mind taking your feet off of my desk, please?


I tend to use "Could you..." mostly if there is some doubt as to whether the person is able to do what I ask. I think it's fairly common in AmE to make that distinction, but I'm certain some folks don't see much difference between "could you" and "would you", so it's not really a rule that you have to follow.


  Could you possibly speed up the process for me? I need to get those permits before next week.
  Could you please speed up the process for me? I need to get those permits before next week.   


I tend to use "Would you..." mostly in situations where I'm asking the person if they would be willing to do what I'm requesting.


  Would you help me carry these boxes please?
  Would you mind helping me with these boxes?


How much more polite does the word please make a request?
I'm a big fan of ZFS on FreeBSD (I've been using it on my home server since before it got stable; bleeding edge, baby!) and I'd like to try out btrfs to see how that's evolving.

Since it's still largely in development, none of the usual mainstream distros have btrfs as an option. I haven't used Linux in a bunch of years, so I don't really know what my best options are for giving btrfs a try.

Requirements:


easy to install
btrfs supported without requiring me to rebuild the kernel


Thanks!
