Here's my two cents. The Magnum case does look very nice and it offers the flip-cover option. However, I actually prefer to have the cover open to the side since mostly I use my x50v in landscape mode, with the display set to real VGA.
I own two of the DS International aluminum cases (see the sticky thread and search for DSI,) the regular case for the x50v with Dell 1100mAH battery and the extended-battery case that accommodates the 2200mAH battery.
I don't own the Innopocket or Rhinoskin case hence I can't say for sure whether the DSI cases are identical/comparable to the aluminum cases from other brands. From the pictures they do look identical. What I can say is this: the DSI cases are less expensive ($16 each) and they do fit like a glove

- not too tight to put in or take out yet not too loose for the Axim to slide without force; and the openings in the case align with the buttons/ports on the Axim perfectly. The entire interior is covered by a thin layer of neoprene so there is no worry it will scratch the Axim. The finish is very good, no sharp edges, everything lines up nicely, hinge pin is tight and just the right length - just a bit shorter than the hinges. Overall the DSI cases are excellent products, especially when the price is taken into consideration.