Wait....so these things only work if you use ghash?
WTF. Nice one Bitmain. Not.
No.... There is currently a bug which is affecting the S4 working with pools which have Variable Difficulty.
I was waiting for a firmware update but I understand the Chinese have been on Public Holiday for the last week so I decided to change from Eligius to GHash.io (which was the advice given last week). At least I am mining at full speed pending a firmware update

But most pools use vardiff. Didn't Bitmain test their units with any pools before shipping them? You should be able to use this thing with any pool you like, especially for that price. Sorry, but that's crap.
Good luck waiting for that firmware update too, from what I've read elsewhere on other Bitmain threads, customers have been waiting months for their firmware updates.....& still not got them.
EDIT: Reading back a few pages, what about this:
I'm a little confused tbh, as ck says:
It turns out the controller is so low powered that it can only process ~30 shares per second which mean that unless diff is set higher, they work their way into a death spiral before diff catches up. Great...
Which to me sounds like a hardware issue - or is it the firmware that decides how much power is provided to the controller?
It's not a firmware issue. The controller hardware they bundle with it is not fast enough to handle running at low diffs, and most pools start at a lower diff for a while before vardiff pushes them up. If they stay low diff long enough the controller never catches up. I gave them a driver code workaround (i.e. hack) to get over this hurdle. It means they'll (appear to) run at low hashrates for a while until the pool reaches a diff suitable for the device. When they say it's a firmware issue, they mean they'll offer new firmware with an updated cgminer to address the issue.
So if it's a hardware issue, no amount of firmware updates will fix it. The only way to fix this is to replace the under powered controller, is it not? Sounds to me like Bitmain didn't research enough & simply threw this thing together & shipped it out without testing it at all......nice.
Hey listen! I'm just an average joe who bought an S4. I've shared my success with GHash in the hope it might help someone else. Carry on with the negativity if you wish but it is not providing anything to this topic! It's all been said. I'm Hashing, I'm happy pending firmware or replacement controller.