Yes,technically it is un-Islamic,worshiping any entity other than GOD is un-Islamic as even the most deviant Muslim will tell you. And its not just the Muslims,every monotheistic creed would have problem accepting it. The SGPC for instance has taken a stand against it.1 and so have many Christian groups.2 In fact, almost all non-Hindus would have a problem with it if they are true to their creed, after all, as Rabindranath Tagore said in his letter to Netaji -
"Of course Bankimchandra does show Durga to be inseparably united with Bengal in the end,(emphasis mine) but no Mussulman [Muslim], christians and Arya Samajis can be expected patriotically to worship the ten-handed deity as 'Swadesh' [the nation]. This year many of the special [Durga] Puja numbers of our magazines have quoted verses from Vande Mataram - proof that the editors take the song to be a hymn to Durga".3
