I've lived in Germany, France, and the UK for 4+ months each. On the whole it's been a wonderful experience and I would be happy settling in any of these countries on a more permanent basis - though that depends on the sorts of jobs I could get there!
Hardest part, if applicable, is going to be the difference in language. Neither French nor German are particularly hard languages for us anglophones to learn, but thinking/conversing in a foreign language every time you want to leave your home becomes exhausting.
Best part, ofc, is immersing yourself in the local culture, food, entertainment, and so on.
Would recommend it to anyone who had the opportunity.