Is it worth doing a poster presentation?
I have some experience publishing in CS, so I'll give you my point of view.


  The conference requires the authors to pay full delegate registration fees as is required for authors of published works. Is it a common practice ?


Yes. In general, every participant is expected to pay in full, no matter what kind of contribution he/she has submitted. You are paying the conference, not your publication. One could argue that this is the main point why many (weaker) conferences even have poster and short paper tracks - to get more people to pay full registrations and attend the conference without having to accept too many papers.


  I was a novice student in the field when I submitted the paper, but have worked a lot in past few months in the area. And I am not looking for any specific inputs into that work anymore.


I should comment that this is a somewhat questionable attitude. Even if you are not planning to continue a certain line of research, hearing what others think about your work will help you a lot in future research projects and papers. Also, I don't think that you can go from novice to can't learn anything in the field anymore in the timeframe of a conference paper review process, so I'll wager that some in the audience will still have reasonable input on your work.


  Is it worth doing a poster presentation in such case ?


I would say this depends on practicalities. Is your advisor OK with paying your conference trip without a full paper to show? Is it far, will the travel be expensive? Is it a top conference that you want to attend for the conference's (and associated networking's) sake? Have you done many presentations, or will it at least be good training?

That being said, from a scientific point of view, most poster presentations are not very valuable. They don't count a lot on your CV (except, maybe, if it really is an absolute top conference), and you will not get that much feedback, realistically.