What this really comes down to, I think, is figuring out how your "gut level" concerns fit into the big picture, and to then put that into terms that the people responsible for the big picture can use to make a good decision.
Finances do matter. Getting your employer to spend money it doesn't have to on network equipment generally means there's less money available to spend on other things that might matter, like making your network bigger, hiring people to help you, or even keeping you employed. If you want to spend more on equipment than the bare minimum, you ought to have a reason. To get anybody else to come to the same conclusion, you ought to be able to explain that reason.
That said, I think it's valid to buy something because you're comfortable with it, and valid to not buy something because you're not comfortable with it. "I don't want to buy new device X because I don't want to have to learn how to use it" sounds lazy, but most of us are busy, and if the device you're comfortable with will do the job for an affordable price, it's generally good not to create extra work for yourself.
Saying "we shouldn't do that because I don't know how" is hard. It may be because something is new and complicated, and nobody has experience with it. Or it may be because you're not familiar with it when lots of other people are. You may have a different specialty, or it may be because you're less experienced than the people they could have hired if they'd paid or shopped around more. But, your expertise or lack thereof is a legitimate thing to take into account when making decisions, as is the likely expertise of people who will have to manage the system in the future.
Unfamiliar network equipment is expensive to manage, whether the CLI is well done or not. Even in a one person shop, you won't yet have encountered the device's pitfalls -- its easily circumventable bugs, the configurations that seem intuitive but aren't, etc. It's going to take you longer to design and configure your networks, and you're going to create problems by doing the wrong thing more often. You're probably going cause some outages, or even buy equipment and then find that you missed something and need to buy something else. If you work with a large team, and maybe even have NOC people working the night shift in another location supporting the thing, it gets worse. All those people have to be trained on the new device, and come up to speed on it.
It's also good to understand the reliability requirements for something you're building. We don't have licensing requirements for Network Engineers, but some other more established engineering professions do. If a structural engineer signs off on a building despite being unfamiliar with some aspect of the construction technology and the building collapses, that can be career ending.
Internet networks that have become pretty important too. If you're building a network where a failure will cause a heart attack victim to not be able to call 911 from their VOIP phone, it isn't good enough to say "I've never seen this piece of equipment but I don't have any reason to think it won't work." If you're building a network to connect some office PCs, the stakes are probably lower.
And, of course, there's also the option of learning about unfamiliar technology. Play with it in your lab. Put it in a peripheral site that can fail without causing too many problems. Get your NOC staff familiar with it. And maybe, in the end, you'll find that you actually like it. That it does something your old hardware doesn't. That cheap hardware lets you afford a level of redundancy, and thus reliability, that was simply unaffordable with you're previously preferred equipment.
But that testing and familiarity has a cost, just as buying expensive equipment does, and just as running unfamiliar equipment does. It's a matter of balancing it all out, and coming to an agreement with your management on what the best strategy is.
-Steve
