I've been watching and reading a lot of reviews this week, and the overall conclusion appears to be that the testers liked it. Some of the "enthusiast" reviewers compared it unfavorably to the iA, especially on the transmissions and suspension, but for those looking for a "warm hatch," the iM seems to be a home run. I personally am very happy with the decisions Scion/Toyota made on feature content--alloy wheels, heated mirrors, and a leather-wrapped steering wheel should be standard on all Scions.
In my honest opinion, straight out of the showroom completely stock with no modifications then no - it is only a "tepid" hatch. Add a TRD exhaust, the proper TRD intake system and the ECU tunes that appear to soon be on the horizon then yes - it would most definitely be a warm hatch especially given that is handles very nicely for a front wheel drive car.
Just to correct that article: it claims that the car came with the TRD intake system, but as can be seen from the photos, it just came with the re-usable TRD air filter only. The full TRD intake exchanges the top half of the stock airbox for a TRD one and features a shorter, more direct, straighter bellow coupling from the airbox to the throttle body. That in itself likely would not count for more power but it would marginally improve throttle response over the existing stock arrangement.
Here in Australia it is generally recognised that warm hatches begin with the Swift Sport. That car has 3 kw less stock power than the Corolla Hatch here but it weighs about 160 kg less. But it's the same deal here as in the US - add the JDM TRD exhaust, the US TRD intake (less charcoal filter which is not needed in other countries) and the Alientech tunes (if and when they ever come) then you would end up with somewhere around the 118 kw mark (around 158 hp). Then it is most definitely a warm hatch. Without the Alientech tune then probably around 108 kw (145 hp) here in Australia on our 95 octane unleaded. In that case you could possible then put forward an argument that it is a borderline warm hatch.
For those interested, the Australian version (virtually identical except rear end suspension is torsion beam) got a relatively good write-up at Performance Drive. There are also two performance tests on Youtube - one for the manual version and the other for the CVT. The performance of the manual version was quite surprising given the specs of the car - it was virtually identical to 1/10th of a second to the 2.4 litre Camry (135 kw) and genuine 2 litre cars such as the Mazda 3 (118 kw). You can even see in the video that the engine is just as eager at the cut-out as it is down low - our version is tuned so that maximum power comes in at 6,400 RPM and I think the cut-out is around 6,600.