As a realtor and licensed contractor I would like to add my two cents. These type of ceilings most often have asbestos in them. The best way to deal with it is to overlay it with 1/2" sheetrock and DON"T touch it. You will have to skim the entire ceiling to make it flat anyway so why not avoid the mess and possible contamination. It will be the same price either way and no one will notice 1/2' change in the height of your ceiling.
I am not sure what area you are putting your laminate or carpet in. Lamnate doesn't do well where water will get in the joints. It swells and looks bad in a short time. I know it's inexpensive but I think it is a false economy. There are engineered hardwoods, tile and stone options for under $5/ft.
As a broker and general contractor I would have to say yes. Be careful about removing it because it will probably be full of asbestos. You won't believe how dirty your ducts will be and I would reccommend having them cleaned as well. You should also have the tank pumped and filled. Don't remove it. If it has leaked you could be on the hook for abating the contaminated soil. Believe me, I have done it at the insistance of a past client and it was really expensive.