HA Soundwave is one of my favourite Transformers in a while. I picked him up for the hefty price of about A$70 while in Japan, and surprisingly I didn't feel ripped off in the slightest.
There's not really much to be said that Magnus hasn't already mentioned, but I love his menacing stance, and I love that it feels like they've tried to do something with every part of the car in bot mode. Yes he does have wheels on his forearms, but it all just feels appropriately integrated to me.
My only gripe is that the gullwing doors on mine always pop off during transformation, otherwise, I would recommend him to anyone!