Switched from oil heating plans to a heat pump retrofit

I've spent the last few months looking at ways to get rid of our oil heating system and the amount of conflicting information online is unreal. Some people make it sound like heat pumps only work in brand-new houses, while others say they're perfectly fine in older homes with the right setup.

While researching options, I ended up speaking with ResTemp Solutions in Cork. What got my attention was that they focused on adapting the system to the house rather than immediately talking about major renovation work, which made me take retrofit heat pumps a lot more seriously.

For those who already made the switch, what was the biggest surprise after installation, good or bad?