For me it was a big leap going from the Rebel T6 to the EOS RP. I did this for a couple of reasons. One, I wanted to move into full frame, and two I recognized that mirrorless is the future, and increasingly the present.
I am not a pro, retired pro, semi-pro, wannabe pro, or spec-sheet warrior. I am just someone who thoroughly enjoys photography and I am glad I made the natural transition into full frame and mirrorless at the same time. I think you will, too. In my case, I could not justify spending thousands upon thousands of dollars for a new mirrorless body and some lenses, before I even knew if I would like the mirrorless tech. And you won't have to, as the mirrorless gear available from Canon, Nikon and Sony is superb and fits a good range of needs.
Surprises? Not many at all really. I do a lot of reading about cameras and photography, so I was aware of some issues that haven't affected me -- the chronic complaints of "overheating" haven't been an issue for me, as this seems mostly to be a problem for video shooters, which I don't do much of at all. If I were into video, I'd buy a proper video camera. And the battery life issue hasn't been a problem for me either, as I am not a spray and pray shooter. I turn my camera off when not shooting or getting ready to shoot. And I carry a spare battery.
My biggest concern was the EVF. I wasn't sure I would be able to adapt to it, but I found it a joy from the start.
In short, if you are considering a new camera, you should go with mirrorless rather than a relic from yesteryear, but look into the lenses first to get an idea of what is available and whether the lenses will fit your needs and pocketbook. Good luck!
