The main difference between commercial and FOSS is you only get security updates for the actual OS and very few new features which you have to pay for and will break your system without spending time to go from XP > VISTA > Win7 etc.. It will break if you switch hardware too. You can't get IE 9 with CSS3 on XP for example, making sites look far worse for all!!
Keeping packages updated on Windows can take forever. OpenBSD has very few errata as the base is very secure. Linux is just a kernel and often comes with many packages with generally a lot of errata per distro even just in the kernel when you eventually find out about them and absolutely requires constant updating and many more restarts. Major changes in packages affect all OSs. In linux you have rolling release like gentoo and arch where everything is updated constantly but things break and then there's debian etc. which hold features back for a stable system but you still have to handle any modified config files which devs have also updated for new features. Fixing that would be hit and miss. OpenBSD provides both debian stable for base and some server packages and rolling/current being the devs preference and for all packages. In fact the opposite to your belief is true once you have your scripts or puppet sorted, so OpenBSD lends itself to updating many systems very well and more reliably than Linux in my opinion. It does take a little more time though for updating a few non uptime critical systems than say using a rolling Linux because BSD is more than just a kernel which has other major advantages especially with OpenBSDs trusted base auditing etc..
