DA is a great investment and good for tackling for bird etching, but really need to use it for more than that to make it a worthy investment, and get your money's worth. I wouldn't be without one.
In terms of sealants and DAs, for those with coatings on their cars, worth bearing in mind that unless you have Gtechniq Cystal Serum on your car, any other ceramic, nano or glasscoat base sealant will be removed if you polish it with a DA. Crystal Serum, which is pro only application, can only be removed with wet sanding, but not the case with other coatings, even if pro detailer applied. So if in removing your etching you will also be removing your basecoat if you have one.