I can see that a lot of people really enjoy giving a home to exbatts, and there's certainly a feel-good factor about improving their lifestyle and watching them develop. They will be a very placid breed, bred to endure overcrowding without fighting, and have lovely personalities. As BYM says, their best egg laying days will be past, that is why they are being sent for slaughter if not rescued, and they will be more inclined to get painful and fatal illnesses such as prolapse and peritonitis because they have been expected to lay so heavily. Also, they will become inclined to laying eggs with very poor shell quality, or no shell at all. However, those that survive the transfer to a normal life can go on laying for quite a while, and make lovely pets, being very trusting and intelligent. Of course a lot depends on where they've been living and what state they're in when they arrive. Some look almost normal and others will be nearly bald - not so good if being rehomed outdoors in winter conditions.
Unless the rehoming idea really appeals, I would myself agree with BYM about getting 'normal' point of lay hybrids for your first birds, for several reasons. Firstly, you can choose a variety of breeds, with different plumage so you can tell them apart, they look an attractive mixture in the garden, and each will lay a different colour egg, (if you ask the supplier about this when choosing,) varying from fawny-beige, through white, greeny blue, and shades of dark brown. The size and shape of the egg will vary between breeds as well. That means you are able to tell who has laid that day, and diagnose any problems with egg laying in relation to the bird concerned. Exbatts will all lay uniform brown eggs. Also, you will begin to get an idea about what type of hen you like, for when Morehens disease strikes, as it will.
Secondly, you will have both the thrill of 'first eggs' from your teenage, 16-18 week-old pullets, and if you get them a few weeks before they come into lay they will have a chance to settle down, finish growing, and get ready for a good laying season in the Spring, where you will have the advantage of all their best eggs in the first two years. You'll also have a chance to examine the birds before buying, and even more important, to check out conditions at the suppliers where they're kept. If conditions are dirty and crowded and the drinking water is filthy, walk away, get them from somewhere where you won't be importing diseases that may dog your flock for years. It's most probable that hybrids will have been hatched and raised up to about 16 weeks in large-scale commercial units, where they will have been mass vaccinated against chicken diseases, and this has to happen at various intervals every few weeks, like with kids. Home-bred hens from small backyard breeders most probably won't have had this immunisation programme, not that that's necessarily a problem, but as mycoplasma is so prevalent in small domestic flocks, it's best to avoid the chance of it if possible. It's possible that hybrids won't necessarily all turn out to be healthy and long lived - I had one young pullet die overnight in the coop for no known reason in my last batch - although pretty tough, they're not immortal - but at least they're not very expensive, it's not like buying a purebred show quality hen for twice the price or more!