I have taken the Aeroline Bus before from Penang to Bundar Sunway, KL and found the experience to be quite pleasant. When I was planning my trip to visit the embassy I realized that Aeroline also goes to the Corus Hotel, Jalan Ampang. The bus station is located in the Corus Hotel, which is right near most of the foreign embassies in Kl and also near KLCC. KLCC is the major shopping area at the base of the Petronas towers.
The Aeroline buses are very comfortable and are fitted with entertainment screens located on the back of each seat. There is a fairly good selection of movies to watch during the ride. A small lunch is also served, as well as water and hot beverages. The bus makes a stop at a rest area where you can visit the bathroom or buy snacks or fresh fruit grown in the area. The trip from Penang to Kl takes about 5 hours.
When I traveled to KL I stayed at the Corus Hotel, so all I had to do was step off the bus and check in. The hotel is 4 star rated, but the biggest selling point to me was the convenience. The US Embassy was about a 15 minute walk from the hotel. I would say that the hotel was average, but I found the food in the restaurants rather good, for the couple of meals we ate in the hotel.
For anyone going to KL, either for the shopping, sightseeing or embassy visits I would highly recommend Aeroline. The bus also goes to Singapore.