In 1998 and 1999 I was working for a consulting company doing largely Windows desktop support. I wanted very much to advance my career to the point where I was working on servers and complex infrastructures, and to that end I pursued the Microsoft Certified Systems Engineer certification. I acquired various training materials, and studied hard. My employer paid for the exams, and I passed each of the five tests on the first try. I was delighted with my accomplishment.
Unfortunately, my employer never moved me up, preferring instead to bill me out to clients as a supremely qualified desktop support specialist. It wasn't all bad, of course, because I was assigned to a team that traveled throughout Europe converting a client's setup from Novell to Microsoft. Still, it would have been nice to use professionally that which I had studied for.
Of course, looking back, the late 90s were the time when Microsoft certifications were extremely easy to acquire. It was possible to earn advanced certifications without ever actually using the technologies involved. Indeed, I was living proof: I passed the various Windows Server exams without ever using Windows Server products professionally.
Eventually my MCSE certification expired. I didn't think much of it. It hadn't done much for me, professionally, and I began to view certifications in general with a fair amount of disdain. If you can successfully do something, your work record should speak for itself. You ought not need a certification to demonstrate that you can do a specific job or excel with a specific technology.
Of course, a certification may be a deciding factor between two otherwise similarly qualified candidates. I don't know that that should always be the case, but I know that it often is. And a certification of any kind can help impress hiring managers enough to at least get an interview, from which one's interpersonal skills and work experience should then carry you through.
In the years since my MCSE expired, I began using Linux -- at first personally and then, much to my delight, professionally. I've used Linux at every job since I left that consulting company. I never really thought much about obtaining any of the various Linux certifications, mostly because my previous experience with certifications had been such a non-starter. But also because I have acquired a healthy body of professional Linux experience to which I can point. In addition, I've been a long-time member of the Central Ohio Linux User Group, and have participated in and contributed to numerous open source projects.
I was somewhat surprised, then, when my employer sent me to RH255 - Red Hat System Administration III with RHCSA and RHCE Exams. The training itself was modestly useful. I entered the class already knowing the bulk of what was presented, but I did pick up a few useful tricks, and it was certainly useful to learn the official "Red Hat Way" for a few things. Most useful of all was getting prepared for the two tests I took on the last day of training.
Had I simply taken the exams without the class, I'm certain I would have failed. It's not that I didn't know the material, but rather I wouldn't have been prepared for the testing environment. I wouldn't have been prepared for the kinds of tasks I was asked to perform. Sure, I could have figured them all out given sufficient time, but the exams only afford about two hours each to complete the objectives.