The response time will vary depending on the 1-Wire chip. For instance the DS18S20 temperature sensor has the longest response time that I know of and it take 750ms to do a temperature conversion. When addressing 1 device on the 1-Wire network the response time does not change no matter how many devices are on the network.
The maximum (under idea conditions) length is 300 meters. The actual wire length you could use will also be determined by how many devices you have on the network. Each device on the network counts as a certain length of cable. I don't have that data around right now but you can find it on the dallas website if you are interested.