Not to split hairs here, but the phrase "there is no god worthy of worship except Allah" leads me to believe that there are other gods, but that allah is the only one worthy of worship.
I also prefer it to "There is no god but Allah" because this strengthens the misconception as has been mentioned that Allah is somehow different from God.
الفوائد المستنبطة من الحديث: 1- استحباب الدُّعَاء عند الهمِّ أو الغمِّ أو الحُزن بهذا الذِّكْر.
No, it is not unusual at all; you can even say something like لا سيارة إلا السيارة ; the fist is indefinite; it means that there is no car at all.
By sincerely stating the shahada aloud before two witnesses, one is considered to have converted to Islam.
قال: اذكر الله تعالى في السراء؛ يذكرك الله -عز وجل- في الضراء.