Guess why I bought this particular model?
Of course I like keyboard, very Apple-like, and the mat screen and further the ease of accessing the HDD and other stuff. However, the main motivator was, that it was the successor of the ProBook 4530s, which, allegedly, is the best laptop computer to be OS-Xed.
I tried the traditional route, i.e. SnowLeopard DVD, and the further steps. I got as far as Lion, and than things stopped working out. Finally, I sort of gave up, installed a linux on the laptop and was happy!
Just lately, something told me go give it a try again. Potentially it was the availability of the latest Probook installer 6.1.11, which motivated the second attempt.
All data securely put on an external disk, I tried my luck. Now, my HP Probook 4540s (Sandy Bridge) is happily running OS-X 10.8.5. Even the dared first TM-backup went straight through.
You may ask, why I am not trying to install Mavericks (OS-X 10.9.1) on the laptop. Well, first of all, I like Mountain Lion in a way. And yes, I was tempted by the fact that 10.9.x seems to incorporate power-handling more deeply. Hence, I tried to boot 10.9.1, but it failed in the first attempt... so I just decided to leave things as they were.
We'll see what the future has in house for the last laptop member of the Sandy Bridge family.
BTW, in order to get WiFi, I exchanged the laptops WiFi-card to one that is supported by OS-X genuinely. This set me back by about €8.-
When I bought it, the ProBook 4540s cost me about €600,- and came with MS Virus7. I replaced the 320GB HDD with a 1TB WD blue (which was about another €100.- at the time).
All in all, I am really glad to have bought this computer. It served me fine under Linux and it seems to be doing a great job with OS-X right now.