Here are my results for London and Edinburgh, disappointing:

Vodafone — no service
O2 — no service
3 — 594 ms ping, 0.93 Mbps down, 0.72 Mbps up
EE — 226 ms ping, 0.12 Mbps down, 0.08 mbps up

With the latency issues on 3, I've actually been having better luck on EE getting consistent internet access.

So to summarize, no high speed internet in UK via this promotion. Must be excluded or broken. I plan to ask for a statement credit. In Germany, however, I got 50 MBPS!!

So, I have T-Mobile with an iPhone 6+ and I've noticed the best performance if I turn off cellular data normally and only turn it on when I need to use internet for something. Otherwise, I notice that connectivity typically drops after a certain period of continued usage.

Have you tried covering your iPhone in tin foil?

A point of reference - TMobile roaming in China no longer seems to support China Unicom, only China Mobile. I was able to use roaming on China Unicom last year.
Earlier in the year, I was unable to connect to China Unicom. Contacted TMobile CS who were surprised, and promised to look into it - but as I was leaving the country, did not follow up.

This is significant, as iPhone users cannot get high speed (3G) connection with China Mobile, only with China Unicom, as a matter of technology.

Just tested and have the same issue now, however the "welcome" message from TMobile in China has changed. Compare the message from Hong Kong:
To the message from the mainland:
It seems like an admission by TMobile that China Unicom access (and with it - 3G service) is no longer available. So, it's "Edge" for data for TMobile users in China, unfortunately. How does "secure WiFi network" have anything to do with TMobile service anyway? :confused:

At least it still routes data through TMobile servers in US, so there is no "great firewall" blocking access to Google etc.

Really no carriers in HK or China with LTE?

any improvement to UK tmobile speed today? :D

Anyone using T-Mobile in Paris?

Date: July 3, 2016
Country: Sweden
Mobile Network: Tele2
Ping: 359ms
Download: 16.94 Mbps
Upload: 0.19 Mbps
Phone: Samsung Galaxy S7 (930T)

I would test it again, but I'm currently in a lower level of a building, and I get poor reception down here.

I landed at LHR on July 2, and I immediately got a text message saying unlimited LTE while in Europe. It worked very well during our 4-hour layover.

I've been using it in Sweden now, and it's definitely faster than EDGE speeds. My data sample is a bit uncommon since the summer house is on the edge of LTE reception, so it gets a bit spotty.

Good to know! Thanks. I'm glad, especially, about the LHR update. I'll be in UK for 3 weeks.

for the people in UK whose speed is slow, can you try different tmobile apn and see? maybe alpha, simple or some others?

In Norway. Using the only carrier with which T-mobile partners here. Telenor. Speeds are 19 MBPS up and 1.7 down

In Denmark now. Getting high speed with all the major carriers. TDC seems the most reliable. Telia seems the least reliable. 3 isn't that fast at points. Overall very happy with the setup here.

Faster than the hotel wifi?

Yes, better/smoother for video calls than the WiFi.

In Sweden now.

Telenor SE: 377 ms ping, 68 MBPS down, 6 MBPS up
Telia S: No relationship
Tele2: 301 ms ping, 0.07 MBPS down, 1 MBPS up (avoiding at the moment)
3 SE: 382 ms ping, 8 MBPS down, 3 MBPS up