Depends on the context and how sensitive the person was. Its text speak for newbie but it comes off as derogatory on how its used sometimes. if someone said "how do i do x" and someone shouts "omg what a noob!" and offers no other feedback, i think it comes off a bit condescending. yeah, i don't know could someone help me or are you there to just mock me?
if someone makes a beginner mistake and goes "hahaha what a noob!" i think that's going a bit far. We were all beginners at something and its not fair when starting off to insult someone. Then again, as some philosophers say, to learn you have to be prepared to look stupid, you have to make those mistakes as its kind of expected/part of the process. Also understanding that people are a bunch of dicks, be better then those people by not acting like one yourself.
if someone used it in the context of "he's a noob at this, could someone show the user?" its not meant as an insult. All boils down to tone and context.
That said, in a working environment (especially a non technical environment) most people will probably roll their eyes. Its not at the same level as someone saying lol in a real conversation, but you're skirting towards that level of embarrassment. Among peers in an informal environment, who are familiar with the term or probably used it themselves, they'll probably not care.