As a family of 4 we recently travelled on the Aeroline Bus FROM Penang to KUALA LUMPUR. It cost us RM60 per adult and RM30 for a child (over 13 yrs is adult cost).
To buy tickets you MUST buy them at the depot which is near the Queensbay Mall (yellow buiding). We bought ours 3 days before travel and booked seats 1A,1B, 2A and 2B - top deck right at the front - the BEST seats to have. Coffee is available at the depot before departure or there is a Starbucks nearby.
The bus is extremely comfortable. We were given headphones for the on board movie but I just enjoyed the classical music on channel 4. They brought around a bottle of water not long after departure and later on a lovely meal of chicken & rice. Coffee came later.
The bus used the express way so the views are a bit boring but the roads were safe. We stopped at Ipoh for 20mins. We grabbed some snacks and drinks.
There is a sitting toilet on board but the space is very small so a larger/taller person would be cramped.
It was comfortable and cheap and highly recommended.
Do make sure your luggage is put onto the bus and get off quickly to ensure no-one takes your luggage at KL.
We were expecting extra costs of RM10 per luggage tag (as per their website) but they weren't worried. They may not take a really large suitcase as their storage space is small. Check first.