After months of redesign rumors, the iPhone 4S debuted last October without any kind of external changes. Much like the new iPad, the familiar-looking handset drew an onslaught of “disappointing” headlines from around the web.

But Apple obviously knew what it was doing. The 4S has broken a number of sales records, and helped Apple sell more than 37 million iPhones last quarter. And perhaps even more impressive, 6 months later, it’s still on top…

BGR reports:

“Checks performed by Canaccord Genuity analyst Mike Walkley and his team found that Apple’s latest iPhone was the best-selling smartphone at Verizon Wireless, AT&T and Sprint in March, continuing a trend that began when the device first launched last October.”

Being the top-selling smartphone for 6 months running on all three of its US carrier partners is quite an impressive feat. Even more so when you consider that other manufacturers like Samsung and Motorola launched flagship handsets during that time period.

Make no mistake though, Apple is going to have a tough time keeping that top position over the next few months — especially with handsets like the Nokia Lumia 900 and Galaxy S III on the way. But what it’s been able to accomplish so far with the iPhone 4S is nothing short of incredible.

Not bad for a disappointment.