I DEFINITELY use hyperlinks. I am actively annoyed by books that don't hyperlink the chapters.
I think, as others have said, it comes down to the reader. Readers who use them will be annoyed by their lack, but readers who don't use them won't be bothered by their presence, so it's best to include them. It isn't that hard -- in fact, if you're finding that part difficult you might want to pay for formatting, because if hyperlinks throw you there might be other formatting elements you've overlooked that will contribute to the professionalism of your book.
(Just a note -- I wouldn't take a lack of customer complaints as an indication that people aren't bothered, as I get very bothered but have never complained because, you know, effort.
Lack of hyperlinks has even stopped me reading -- especially short story anthologies; sometimes I'll open it up intending to browse through and read the stories out of order starting with the authors I've heard of and am excited about or the titles that sound interesting, and there are no hyperlinks so it seems like too much work and I go to another book I'm reading instead. I also read on many devices and they don't always sync up properly, so I use them for novels as well. AND I'm the type of person who flips back to check my memory of scenes when a twist happens. I can easily imagine a scenario where I stop reading a novel because it's too much work to find my place again -- I'm always reading about 7 books at once so I accidentally put books down and don't pick them up again all the time, and if I click to other books enough times because I don't feel like figuring out where my place was by doing a binomial search with locations, I may very well do that with an electronic book as well. PLEASE include the hyperlinks.)