Sometimes when counting the seconds while exposing or developing my print, I lose count and either trash the print or just guestimate what second I should be on. Sometimes I screw up so badly I end up with a print that's too bad even for my low standards; that makes my darkroom time less enjoyable and productive
If I had a timer, I'd probably ocassionally set it wrong or lose track of time with it somehow*. That would make my darkroom time less productive and enjoyable.
I'm being a little cantankerous here, but I think a timer would be nice, and I wouldnt turn down a good deal if I found one and actually had a bit of spare money.
I have a surge protector that my lamp and enlarger plug in to. It sits on a table (the surge protector) next to the enlarger and is plugged in an outlet under the table. When I'm ready to expose a sheet, I flip the switch on the surge protector and the enlarger light comes on. I count the seconds until I get to however many it takes to properly expose the paper (when I contact print, there's enough light for me to see the clock as a guide if I lose count. counting 20 seconds is so easy I can do it 99% of the time without screwing up).
When developing, I just listen and count two minutes, which really isnt too hard if I concentrate. I might be more productive with a timer, but I'm a bit of a clutz, so that's just something else for me to try not to break or set wrong.
*at the school darkroom, we have enlarger timers for each enlarger. There's a Gralab timer on a table at the end of the sink. We usually set that to 59:59 minutes and let it run until it stops and then reset it. It's pretty easy even for beginners (at least at UAH) to watch the timer for a few minutes to make sure the print is fully developed and fixed. However, some uf us (me included) have got to talking to each other without realizing the paper has been in the developer for 5 minutes