Looking at and having to edit with contact sheets. Ugh. I hated this. Trying to look at 36 little images with a loop and figuring out which were worth printing. Then you tried a print, only to find that, yep— it wasn't worth printing. I remember thinking that there has to be a better way. Now you can look at them big as a screen, side by side, whatever. Slight improvement? Hell, yeah.
Cleaning up the darkroom (chemicals, trays, sink, developing containers, et cetera) after every session, whether it was 20 minutes or 8 hours. That got old. I remember thinking that there has to be a better way. It's called a computer and a screen.
Either the extreme expense of having a lab develop film for you— or developing it yourself, which was real tedious. I remember thinking that there has to be a better way.
Having to check how many shots you have left on a roll. The guilt of thinking that you have just shot 7-9-12 (more?) rolls of film, and the cost and tediousness of dealing with it. I remember thinking that there has to be a better way. There sure was.
Having to stick with one ISO for at least a whole roll of film (like 100, 400, or 3200). Not to mention that anything over 400 ISO was only good if you considered it fine art. I remember having to juggle two cameras at a wedding— either a combo of low and higher ISO, or color and B&W. I still keep two great cameras with me (you have to have a back-up camera)— but one with a 24-70mm f2.8 lens and one with a 50mm f1.2 lens, so I can quickly get appropriately different kinds of shots. Much better.
Speaking of weddings, having to change a roll of film right when there is a shot to be had— yeah, that sucked. I could go on and on, but these are some of the biggies that I really don't miss at all...