I just did the upgrade and it took me a little bit to wrap my head around the new installer and the Configuration Centre, but once I got that understanding from support, it was very much worth while. The hotfix apply was simple, the Web Desk has been touched up and is a lot better in my opinion. I haven't had time to do a lot of design in the 7.5 version, but the few pieces I did do are like night and day from 7.4.
I have just upgraded our test system so far and I much prefer it. Mostly because the webdesk and self service portals looks so much more polished and professional now. I haven't really got into the nitty gritty yet as we haven't gone live yet, but I'll keep you posted!