Never a good idea to be negative about current job when going for a new job. Remember that the interviewers usually dont know you personally, so you could inadvertantly come across as either a generally negative unhappy person or someone who finds it difficult to fit in.
You are always better taking the approach that the new job you are after is a better one than the job you are leaving and that is the reason for seeking the job. You can always find a reason why it is better e.g. better pay, more suited to qualifications, better prospects, more interesting work, more challenging work etc. etc. etc.