(Spelling in the original note corrected, but otherwise, this is as it was received)
I have a problem in my current project, I tried to drive the design to a children-kind of interface, making the buttons big and with different shapes and colors, using big and round letter fonts, etc... The point is that the interface is to be used by 18-30 year old persons, and I found out that, for example my colleagues, feel uncomfortable with such a design, I felt they expected a more office-boring-small font-professional look interface.
My question is, given the context, what is better, to maintain a (supposedly)well designed program, or to make it the way they like it? Is the first-impression so important, that the emotion it causes in the user, makes it easier for him?
You may have written a usability-centered interface, but that is not the same as a user-centered interface. You have shown a complete failure to understand what user-centered design is about.
You ignored the most important part of design: to understand your users. If, as you say, you were designing for 18-30 year olds, then why did you think to use what you call "a children-kind of interface." That makes no sense. 18 - 30 year olds are not children. Of course your colleagues hate it. I would too. And for you to say "I guess they want it boring" is to insult them.
User-centered design means working with your users al throughout the project. First, study what their real needs and behaviors are. Then use rapid prototyping methods to see if you are on the right track. Design and test, repeatedly. From your description, it sound as if you thought about the problem, decided upon your own solution, built it, and then were disappointed that it wasn't liked. So you insulted the users. Bad, bad, bad, bad.
Your question is also wrong. You ask if it is better to do a well-designed program or to do what users like. How peculiar. Why do you think you have to chose between those options?
If you were to work with your users from the very beginning, you could offer both. Indeed, you have not shown me any evidence that what you designed was well done (just because it has big buttons, etc., does not mean it is well done). Well done means your users both can use it without difficulty, and also with pleasure. You have clearly failed on the pleasure part and I see no evidence on the usable part.
Sorry to be so mean and nasty.