This weekend marked the first time that Sprint was ever able to offer Apple’s popular smartphone to its customers. The carrier’s been waiting for 4 years now to gain access to the coveted handset.

But even though the new iPhone helped the company set a single-day sales record, the weekend launch didn’t go as smoothly as planned. Several Sprint subscribers have been complaining about the device’s 3G browsing speeds…

In our speed test showdown last week, we pitted iPhone 4S handsets from Sprint, Verizon, and AT&T against each other to compare 3G browsing speeds. The results were pretty clearcut, and Sprint was by far the slowest carrier of the three.

And it seems like the test results echo around the country, as several Sprint customers have voiced similar complaints. In fact, so many have come forward that Sprint felt the need to make an official statement. Here it is via PCMag:

“As always, Sprint is carefully monitoring the performance of the 3G network. We are looking into a small number of reports of slow data speeds when using the iPhone 4S, however there are also reports showing that Sprint’s network is the fastest, such as the Gizmodo report that came out earlier today. Speed tests represent a moment in time and are subject to many variables including weather, time of day, device, and proximity to a tower. Sprint will continue to monitor the feedback we are getting from our customers and will investigate and resolve any issues that may arise.”

As MacRumors points out, it’s unclear which Gizmodo report Sprint is referring to. The gadget site’s speed test returned the same results that ours did, with Sprint showing dramatically slower data speeds than either of the other two carriers.

So even though it still offers the unlimited data plan, Sprint’s wireless service doesn’t come without its caveats. It looks like if you frequently use your phone to browse the web outside of a Wi-Fi network, you may want to think twice before going with the iPhone’s newest carrier.

Any Sprint customers experiencing similar problems?