I used the 598's for a while and quite like them. Maybe a little shy on the high end, but they're super comfortable for long listening sessions - and I mean both wearing them and how the sound doesn't become aggressive or tire you over time. I since moved on to Meze 99's as my main cans, but those Senn's are great for the price.
I have some Sennheiser HD 599 SE that I use every now and again. I don't use them all that often, but they sound fine to me. I usually only use them when streaming a podcast or something.
I also have the 598 that I still use every once in a while as well. Never had any issues with it - great sound. I've always prefer open over closed though.