I've been setting up my Raspberry Pi again. Last time I used it to monitor a server room door by taking webcam pictures and emailing them to me. Now I'm considering if it would work as a WiFi access point.
Downloading and imaging the latest Raspbian to an SD card worked fine but I kept having problems. Works fine initially but the next morning I'd see massive filesystem corruption (segmentation fault, signal 11 etc. just doing an ls etc.). Maybe a bad SD card? So, try another: same thing the next day. Maybe my Pi is broken?
Turns out to be a poor power supply. I'd plugged it into a micro-USB phone charger that just isn't giving out the right power (needs a good 5V). Try a better supply and it seems fine now. This shows how critical a good power supply is!
How critical? Well, the wrong type can kill you, so be careful. A while ago, a Chinese iPhone user was supposedly electrocuted and died, probably using a poor (and fake) charger. For a detailed look at this, see Ken Shirriff's blog.