You should be able to load into activities faster, access your menu/inventory faster, not get "stuck" in "transition boundaries" in strikes, and do things like preview shaders more effectively while loading. Now, is it like 2 minutes HDD reduced to 10 seconds SSD? No, it's not that dramatic... but everyone I've talked to and my own personal experience has been that it is a pretty significant difference. I often load about 30 seconds faster than HDD users. If you feel like it's genuinely "worse" I would seriously wonder if there was something wrong with the install or the drive. Did you buy some cheap drive from a questionable source?

SSDs only affect load times, not frame rates. Even so, it doesn't affect load times that much.