Today, at CES, Intel announced a multi-year partnership with Motorola, a new phone from them featuring Intel Atom in 2nd half of 2012, and also a Lenovo phone with Atom that is coming out in Q2 this year. The Atom processor is pretty much the same old Atom processor we've gotten used to regarding performance, and has only been slightly optimized for power consumption.
Its idle consumption mode is still several times more inefficient than an ARM processor, which means your phone could be running out of juice within a few hours, even if you're not using it. Unlike laptops, that people usually shut down, phones and tablets are just kept in idle mode, and it can last you for days. This is made possible thanks to ARM's ultra-efficient chips. Atom won't be able to last that long.
On the GPU side, it apparently uses a PowerVR SGX540, a chip that has been used in 2010 in the Galaxy S. This means that by the time it gets to market, it will be 2 years old GPU. The other GPU's that will be in the market around that time should be around 5x more powerful than that GPU.
Also, we should start seeing dual core Cortex A15 chips from Samsung, and dual core Krait chips from Qualcomm, both of which should be more powerful than Atom with just a single core, and yet they will have 2 cores, which makes them even more powerful, and much better at multi-tasking. The lack of a dual-core will be noticed on devices that are supposed to be high-end, and it will be especially noticeable on tablets, where you're much more likely to multi-task.
Perhaps worse yet, is the fact that Atom is still using fans to cool down. Imagine taking out your phone or tablet in public and hearing a buzzing sound from it all the time, while you're using it. Wouldn't that be pretty awkward?
Besides all the technical issues, it's also worth considering the market issues. ARM completely dominates the smartphone and tablet markets. Even if Intel is a big chip company, that doesn't mean they can just walk into a market, and start being a strong player. It's also pretty strange that any manufacturer would risk having Intel enter the market, and do with them what Intel has been doing for years with PC manufacturers, keep prices very high on them, and pushing out competition, for which they've even been fined over $1 billion in EU.
My conclusion is that this Intel Atom would not only be undesirable by the market, but it won't even be able to compete very well, not just in power consumption, but also in performance. Krait and Cortex A15 should easily beat Atom, which means there are not many reasons why you would even want an Intel Atom in your phone or tablet.