I also had my Mk1 player hooked up to the permanent power. It worked well except it had the following issues:

- Leaving the player in the car for a long period of time (such as a weekend) can be a drain on the battery. The CPU is still running when it's in standby mode, so it does draw a certain amount of current. You shouldn't ever leave it in the car anyway, because it can get stolen if you do.

- You will have problems with "pop" sounds coming through the amplifier when you turn the ignition on and off, especially if you are starting the car engine while the player is playing. You'll need to be mindful of things like making sure to put the player into standby mode before starting the engine.

- You will occasionally run into boot-up issues if you put the player in the car and then start the engine while the player is in the middle of its boot process.

But if you're willing to work around those issues, then you are welcome to leave it hooked up to the permanent power. It has the advantage of letting you listen to the player even with the engine off.

Ideally, of course, you would have a Mk2 which has a separate ignition-sense wire and can work around all of these issues and give you the best of both worlds.