It's customary for manufacturers to try and build up hype for their newly launched smartphone by talking up their sales numbers. Samsung made no exception to this, saying that its new Galaxy S5 flagship sold 30% more units than its predecessor on launch day.
Back then many expressed doubts that this is more due to the far wider launch - 125 vs 63 markets, while demand in developed markets has actually stayed pretty much the same. It's a common assumption that the high-end segment in those has reached saturation point and growth is next to impossible to achieve.

Yet today, a new report from the major UK retailer Phones4u points in the complete opposite direction. According to the press release the Samsung Galaxy S5 saw twice the sales of the Galaxy S4 on launch day and it has been enjoying similarly high interest since. While neither the retailer nor Samsung have provided exact numbers, the statement is still pretty impressive and bodes well for the success of the smartphone.
Samsung should be releasing their Q1 financial report shortly, but that one won't include the Galaxy S5 sales as those only started in April. However, we are still expecting to see some clues about it in the guidance for the second quarter and we should get a dedicated announcement when the latest flagship hits 10 million sales.