Hi,
I've just been through this myself, did tons of research (well I was at work). I eventually decided to get a GoPro. You're right, there's loads of attachments needed, but that seems to be true regardless of make. As above you can pick up cheaper compatible stuff if you look around.
If you're doing track days, be aware most operators won't let you use a suction mount inside the car - they usually want the camera fixed mechanically to something or other. For external fixing I believe most TDOs are happy with a suction mount and a secondary tether.
SilverSurfer's right, the internal mic on a GoPro is poor, so I've ordered a cheap external mic. This means I can trail the mic out to the boot and pick up the exhaust noise with no wind interference, and if I do want to get the sound from the cabin the quality should be better.
Also, as Ginola says the GoPro is compatible with Harry's Lap Timer which is quite impressive. Coupled with the BT device and an external GPS, you can get very accurate lap info (after the event of course
) overlaid on your video.