I don’t think it’s necessarily pretentious to sign off with MLIS or whatever degree you received, but I do wonder what people’s motives are. I understand that getting a degree is work- otherwise everybody would have done so- but getting a MLIS is not the same as an MBA nor a JD, PhD, or a number of other degrees. (Many people think it’s a relatively mindless degree, which with I can’t totally disagree.)
Have I worked hard to earn my MLIS? Yes. Am I proud of the work? Yes, but mostly because it’s made me a better library staff member and I think it’s improved the quality of service I provide our users. When I have the degree, will I put it on my business cards? No, but it’ll be on my resume. I say this as somebody working in an academic environment where most people have advanced degrees. If you’re a “Librian” here, you have a masters. If I worked in a different environment where I might need to justify myself and expertise more, then I’d probably think differently. As it is though… people will know I’ve graduated by my calm demeanor and pleasant smile at the reference desk, as opposed to my normal haggard look.