Having recently invested in CCTV and tried various options, I have found this to be the best combination of features/stability/price - for an indoor camera. While there is an enclosure, the size/cost makes it uncompetitive; if you want an Y-Cam for outdoor, go for the Bullet.
Size: pretty compact, with built-in WiFi, thus you only need a power cable to install it somewhere. It is quite discreet and can be hidden if you want covert surveillance.
Picture: not HD, at this price you cannot complain; as it is designed for night/IR use it does not have an IR filter thus the colours are not what you'd expect. VGA @ 30FPS is the max, with 2 smaller simultaneous streams (QVGA, 170x120) for other uses (remote, 3G viewing).
Night Vision: IR LEDs are pretty powerful and can illuminate over 5-6M which is sufficient inside; 'moonlight mode' uses 4 frames to generate 1 better frame works well though reduces FPS by 1/4 (could have pipelined it and still use 4-more frames and still maintain FPS).
Storage: this version includes micro-SD slot to save a continuous stream or just alarms (video/pics). While you should naturally FTP/NAS the video/pics off-site for security, the WiFi/Internet connections can always fail so you should save locally also.
You can also stream to the various Internet sites though some will eventually charge you; at least you are not forced to do so in order to see video/pictures remotely as one vendor does.
Connection: Ethernet (not POE - see other model) and WiFi (not N or dual-band) is good at this price range.
OS Support: Can be configured by either Windows & MAC clients now and can also view remotely on Windows, OSX and also iOS, Android phones via free applications from Y-Cam though there are better apps in the respective markets for a few pounds.
Firmware: Y-Cam does release firmware updates regularly and has added new features, though they are slowing down and products older than 1-2 years are started to be left out. So it may be an idea to wait for the replacement model unless you need something now.
Stability: I have 3 different Y-Cams and they are stable, though over WiFi they do require pretty strong singal. Some models tend to reboot when the connection breaks requiring the use of Ethernet/PowerLan adapters.
All in all, I haven't found a better indoor IP camera than this at this price; the Panasonic range does feature models with better picture quality (higher resolution, better low-light performance, no need for IR LEDs) but they are far more expensive. You can get the cheaper model if you don't want SD card storage.