I am guessing resident expert Dolphin is a Malaysian, so I will try putting a different perspective as an American who is a frequent visitor to Malaysia.
The special high fare taxis I have only seen hanging around tourist venues. Last time I saw one was at KLCC.
Someone was asking about transport to Genting. It has been a number of years since I have gone, but I think the best option is the share taxis from Puduraya.
If you like using priceline.com, I have used the name your own price function to get the Renaissance, near the KLCC, for USD 44++.
No problems with monkeys at Batu Caves. I have been there twice.
Pulau Tioman I think is a little disappointing, if you have been to beaches in Thailand or the Philippines. The only advantage it has is that it is close to Singapore. For the guy who was looking for an outing from KL, I would do something else.
Malaysian registered cars can only spend a certain number of days per year (can't remember, think it is ten?) in Singapore. So if you want to take a rental car into Singapore from Malaysia, you can't rent in Johor Bahru, undoubtedly it has been in Singapore all of its allotted days already. But if you rent in KL, it should be OK. This saves you a bunch of money as rental cars are much cheaper in KL compared with Singapore.
I agree with Dolphin that Malacca is worth a short visit. Nothing is spectacular, but you can try their food, and it is cheaper than KL. I had a pleasant experience last time I was there. A tropical bird decided to visit me. He came up to my 6th floor hotel room.