Bus from Penang to Kuala Lumpur?

I wish to travel from Penang to KL by bus in May with my wife, I found a website: www.ticket4u.com.my through which I can purchase tickets online. I will be staying in Tanjung Bungah (Flamingo by Beach) , the boarding point given for Nice bus service is Bukit Jambul, Please advice which is the best service to use and is it safe to book from this website. Is there any other website from where I can book the bus travel. Also, this website offers some discounts to members and membership costs RM10.