I think it all depends on the person. If you are a positive thinker you'd see someone imitating your work to be an indication that they admire your work and have therefor been inspised by it. However, for people who think negatively and are possessive of their work, imitation is a big turn off. They just can't take someone else following their ideas. Moreover, some people just imitate others but don't give them their due credit. They keep denying that they were inspired by someone's work and that accounts for the similarity between their work. In any case if someone imitates you that only shows that they like your work or they wouldn't copy it. So in my opinion imitation is a form of flattery indeed.