Hello!
The last experimental I got was back I think, in November. If I download the latest experimental, and copy/paste my saves in, will that be a way for it to work so I can keep playing with my current character? And, if so, can I expect any weird stuff happening?
The devs are trying to maintain backwards compatibility as much as it possible. I think you can upgrade with no problems, but I still recommend you to backup your saves.
We always say try it but make backups if your save folder first.
If something goes wrong it’s a bug and please report it.
I’ve had a character for the better part of 2 years, that has been across at least a dozen experimentals, the worst case you can simply recreate them using debug in the new client if its breaking
okie thanks I’ll give it a whirl! 
Just don’t do what I did and allow your character to be underground in your last save… makes you spawn in the middle of underground-surrounded-by-rocks nowhere.
ahh ive had that, basically you last save was under the ground, when that happens enable debug and use the long range teleport option then simply use the move up key until you are on level 0 (bottom right on the map) any minus number indicate you are still under ground)