Is Sufism different from Islam?

Some people say it is a part of Islam and some say it is a different religion altogether.What is right? I am so confused! There are some Sufi poets that have denied Islam altogether.So, any Muslim or Muslimah out there or someone who studies Islam, help!
http://www.rim.org/muslim/sufism.htm

"It concludes by saying that:
Reflecting on the evidence presented, and conclusions given, we see that to assume Sufism, with its radical concepts, is a legitimate part of Islam introduces definite problems for anyone who then attempts to try to defend Islam as a logically coherent set of beliefs. For Sufism not only points to a lack of spirituality in Islam, but also contradicts orthodox Muslim teachings - in the process clearly opening the door to all the world?s religions. "

And, I respect Islam but I am not a Muslim.

Sufism is a mystical sect of Islam. Nowadays there are varieties of Sufism that aren't necessarily Muslim (like Universal Sufism, for example), but barring those new types of Sufism, they're all part of Islam.

for example Malena cladding rum . coming from Zoroastrian background.his books are full of Islam but inside it you can see shirk,beliefs coming from Zoroastrians,bidah (innovations)

result .although Allah and Islam is in their mouths it is hard to consider them as Muslim.For example in Islam you worship and you think Allah sees you everywhere .Sufis say that you should worship like your shaikh is seeing you everywhere so sheikh is their second god.result :failure.sicknesses coming from hindu,zoroastrian,shaman traditions


they were heretics .after mongol invasions they controlled muslim masses and you know the result

i am very respect to Sufism.

this is the for instance:

http://en.wikipedia.org/wiki/Rabia_al-Adawiyya