Those who are probably worried most are Nokia, Sony-Erricson, Microsoft and Palm.
Nokia may be losing its cachet in the high end phones, but it is taking a different strategy in that it's bringing Symbian to lower end phones like the 5530, while also working on the higher end. At the end of the day it is the lower end phones that sell in huge volumes, so I'd say Nokia is not too worried. Symbian is still a huge player in the phone market.