Improvements to the Softbank Network

Softbank's "Platinum Band" service went live on 25th July. Platinum Band is Softbank's name for the extension of their 3G service to include the 900MHz waveband. So what qualifies this as "Platinum"? Until now, Softbank has been at a distinct disadvantage to NTT Docomo and au by KDDI, in that it lacked at low-frequency band for 3G services. Softbank only had 2100 and 1500MHz bands, while Docomo and au also had 800MHz spectrum. The advantage of the lower frequencies is greater penetration, particular in rural or mountainous areas and inside buildings. The upshot was that Softbank gained a reputation for poor connectivity, so much that when au acquired the iPhone, its main marketing strategy to differentiate itself from rival iPhone carrier Softbank was to question the point of a smartphone that can't connect to the internet because of poor signal.
Like many others, while I was excited about the prospect of an improvement to Softbank's poor connectivity, when the 25th July came around and the Platinum Band supposedly went live, I saw no difference. Checking Softbank's homepage, it appears that the rollout is an extremely gradual process. The current states of Softbank's various (and confusing) services can be found here. Even some parts of Tokyo are still not covered by the service.
Other than the slow rollout, a further problem is that most phone models on Sotbank sold before this summer do not support the 900MHz band. Notable exceptions are the iPhone 4(S) and the HTC Desire (X06HT / X06HTII). Alternatively, most international smartphone models support this band, so if you are using a SIM-free phone, then chances are you will benefit from this improvement.
While the Platinum Band is supposed to bring improved connectivity, hopefully meaning less dropped data connections and less waiting for a connection before your page starts loading, what it does not promise is improved speed. For data speed, there are a multitude of related technologies in play:

• 3G: Also known as UMTS or W-CDMA, the basic data network technology in use today. Can reach speeds from 384kbps to 2mbps. Supported by Softbank's Platinum Band
• HSPA: Softbank calls this "3G High Speed", allows data download up to 14Mbps. Most modern phones support this as well as 3G
• HSPA+: Also know as "Evolved HSPA", Softbank is introducing this on the Platinum Band and also on the existing 2100MHz frequency band. Allows download speeds up to 21Mbps. Not too many phones support this.
• DC-HSPA: Softbank calls this "Ultra Speed", and it stands for "Dual Cell HSPA". It doubles the speeds of HSPA, allowing downloads up to 42Mbps. Uses the 1500MHz frequency band on Softbank. Again, few phones support this.
• LTE: "Softbank 4G", up to 110Mbps download in the 2.5GHz spectrum. As yet no phones support this, only mobile wifi routers.

Depending on your phone, you may be able to take advantage of faster speeds. On Android, you can see your connectivity next to the signal bars, where you will generally see either "3G" or "H" (for HSPA) indicated. If you have "H", you are on the "faster" connection.
I recently upgraded the OS on my phone to Android 4.1 (Jelly Bean), specifically the CyanogenMod 10 version. In this latest version, they have added support for further icons; now there is a "H+" icon (for HSPA+), and a 4G icon for LTE or DC-HSPA (in the USA DC-HSPA is marketed as 4G, although it doesn't technically qualify). Since updgrading, I have occasionally noticed that I am getting an "H+" indicator next to the signal bars. At first, I thought this was a mistake or a bug. Then I noticed that it was mostly in subway stations, and I figured that Softbank had prioritised stations in their network upgrade process. So I decided to run a couple of tests using the SpeedTest app(repeated multiple times to make sure nothing was anomalous), and here are two representative samples:
HSPA Network ("H"):

*After the test, the connection dropped to 3G, hence the "3G" displayed in the status bar.
HSPA+ Network ("H+"):

*As above, after the test, the connection dropped to 3G, hence the "3G" displayed in the status bar.

As you can see, neither network comes close to reaching the theoretical maximum speeds, but when I can get an HSPA+ signal, the network speeds are around twice the best speeds I can get with plain old HSPA. And you can really feel it - web pages and Facebook load in a flash on HSPA+. The only problem is, I haven't yet found anywhere outside of Tokyo Metro subway stations and a couple of select (underground) stations on the Tokyu line that have it. I really hope Softbank rolls this out more widely in the very near future.

iPhone 4S users, if you look up your phone specs on the internet, you will find that it supports HSPA+. However, Apple used an older generation Qualcomm radio that doesn't support the full HSPA+ spec, so even with HSPA+, you still only get 14.4Mbps speeds - in other words no improvement over HSPA. This was a big controversy in the US, because AT&T had Apple change the icon for this to "4G", even though it is nothing of the sort. But for real HSPA+ support, you'll have to wait for the iPhone 5. For DC-HSPA support, you'll have to get an Android, although as I mentioned, even with Android there are not many phones supporting this technology yet. LTE is another kettle of fish altogether, which I am avoiding for now, but suffice to say, phones from one country have a 99% likelihood of not working on another country's LTE network, so from the point of view of the SIM-free enthusiast, it's currently more of a troublesome technology than an interesting one. For LTE, buy domestic and use domestically.