Katie i've been eyeing one of those cases up because... well I suck at making stuff. Anyway are those good for more oddily shaped mini's like Assault Marines or the fatter based Terminators?
Yup, they hold just about anything actually. The only things I haven't been able to make fit in there nicely are Monoliths and Defiler/Soul Grinders.
You can fit tanks and such on the bottom row if you take off their turrets and don't mind using a bit of force to shut the lid.

My case is so full right now (I have six tanks in the bottom row, plus three Dreadnoughts, a couple Attack Bikes as well as arms for the Dreads and turrets for the Preds) it's an actual struggle to shut it. It seems like it'd damage the models inside, but instead it just holds them very snugly. Once I kicked my case down the stairs by accident (I was carrying a laundry basket and didn't see it) and every model was absolutely fine upon inspection. Totally worthwhile investment.