Two out of the three major iPhone carriers in the U.S. throttle data speeds of its top 5 percent unlimited data users.

It started with AT&T terminating its unlimited data usage plan, but giving users who were still subscribed to the plan an option to continue. A year after this, AT&T announced its plans of throttling speeds the top 5 percent data consumers on these unlimited plans. Early last year, Verizon followed AT&T, with a similar plan to throttle users.

According to a report last month, AT&T was throttling down top 5% of users to 2G speeds.

Is it really that bad? App Advice took a look at how bad AT&T’s throttled speeds and how it impacted the users experience.

Here are some of their findings:

• Throttled download speeds went as low as 0.06 Mbps, as compared to standard non-throttled download speeds of over 1 Mbps.
• The upload speeds were comparatively closer, with the throttled device getting 0.49 Mbps and the non-throttled device getting 0.70 Mbps.
• The ping times were similar at around 100 ms.
• For everyday applications like Maps and Safari, there was a stark difference between the load times. These apps were effectively unusable on the throttled connection.

Has AT&T throttled your 3G data connection? Are you also seeing similar drop in download speeds?

[via App Advice]