The first iteration we rolled out in 2008 was horrendous. You couldn't move your mouse without a popup. It was like being trapped in one of those never ending spam websites. We put it up with it for a year and hated it. Then CA actually listened and made a few changes and suddenly the SD was actually really helpful. I found myself telling people to please open me a ticket (which i don't do for the current software we use (new firm) Footprints.
So i like that CA listened and made changes
Minimal use of popups and easy navigation
System was fast even though we did not throw the best hardware at it
MAJOR FEATURE: you can expand the ticket and see the majority of its contents without clicking into it. Most tickets are 2-3 sentences so this saved a ton of time.
Color scheme wasn't great and occasionally hard to read though you could mostly get by since it could be resized.
After the upgrade I really didn't have a ton of problems with Service desk, it was useful.
I last used it in 2010 but it was the only system i've used to this point that I was actually happy with using. It was responsive without needing a ton of horsepower, it was flexible in terms of new categories/groups/notifications/etc, but even more so the developers actually listened and changed the UI which was terrible to something that was actually quite good in the end.
I have not touched the product in 5 years though so please do your due diligence.
We used it for a 1400 employee primarily IT workforce so tracking tickets was necessary. We did wind up using it for problems as well (items that take more than a few weeks to resolve or that affect more than a handful of users). The version we used in 2010 was very well done.