What's your biggest surprise in hifi?

SET and horn speakers

How important a tonearm is in the reproduction chain, and how great a really old turntable (Garrard 301) can sound.

"4. That some have thousands of records and keep buying more."

They're like tribbles!

"That stock fuses degrade the sound so spectacularly."

Nelson Pass once told me to change the input fuses in my Adcom GFA535 to 5amp ceramics. Just wow!

Agree with totem395, biggest surprise over the years is how important, and in some cases fundamentally limiting, your listening room can be.  Good kit in a great room can often sound way better than a great kit in a compromised space.

And how manufacturers specifications or reviewers measurements can/must often be thrown out the window once you combine a piece of gear together with components, wires and in a space that are different than where originally measured.

Oh, and how important power cords can be to overall system performance.

1. How much money some people are prepared to spend on components/cables/etc... -  in the pursuit of "audio nirvana"

2. How much related knowledge some people have acquired about this obsession - thanks Almarg! - just one of many on Agon.

3. the frequency with which some people change components - like changing socks

Boofer - + 1 on the Nait - especially when you treat it to great cables :-)
I have the 5i mk II with the passive front end - amazing!
- I WAS considering the Supernait - thanks fro the info :-)

Regards...