Hey, the Arduino can do NTP, and I managed to get the web server up to an almost-reasonable speed. It can even plot graphs. For a while I had one plotting weather graphs and web-serving the results.
But really an Arduino wasn't the best solution for a home web-server. And neither was my old, unloved, noisy and power-hungry PC. This is where the RPi will be perfect: small and economical, but powerful enough to run data analysis software, web-servers, and plenty of other things.
The argument about learning Python et al. is I think only half the story. After all, you can install a Linux virtual machine on almost any modern PC and hack away to your heart's content. The point of the RPi (IMHO) is that once you've made it do something, it's cheap enough to install it somewhere and leave it doing that thing: whether it's flashing lights, watering the garden, web-serving data from your home weather station, turning your TV into a digital picture frame, or a zillion other things. In that sense it's similar to the Arduino, but the possibilities it opens up are somewhat different.
Now the developers of the Beaglebone, Chumby and other boards can justifiably feel a bit peeved about all the attention RaspberryPi is getting. Many are arguably more powerful than the RPi. But the RPi people have got a lot of things right - in particular the connectivity, and the price. I think they've reached a certain threshold of appeal, and that's the reason for their success.