Frame bursting helps in mixed mode environments. For. ex: If you have Wireless G and wireless B linked to the same router, frame burst helps in this type of mixed modes. The performance and bandwidth is high in wireless connection in single device.
It works well when a single device is transmitting at a time. That means not many devices at a time.
It may reduce the performance when too many devices are connected to an access point. Usually 54Mb bandwidth is shared between the devices connected to an access point.
All other devices will be burdened, if one device hogs the channel. Frame burst helps to receive/send large burst of data by letting a single device hog the channel,
Although it have some advantages, why it should be disabled some times? Because, turning on degrade the performance, so Linksys does a normal approach to disable it by default.
The user should decide whether to turn on the Frame burst or not depending upon their usage. If you need faster performance, turn off frame burst on your Linksys.
If you want to connect too many devices to the same router, it is recommended to disable frame bursting. If you are connecting to a single device or less number of devices then you can enable frame bursting to increase the efficiency.