I normally have a good 3g connection all the time and have rarely turned on the wifi feature of my Blackberry Bold.
Is there a pro or con to always having the wifi running in the background? Does this somehow impact battery life or consume resources that might slow down the responsiveness of the device?
If you have wifi on but it's not connected to a network, it will drain your battery because it's constantly searching for a network to join.
If you aren't connected to a network, don't leave wifi on.
If battery consumption is an issue for you, turn WiFi off if you're not in a WiFi area. But keep WiFi on whenever you are in a WiFi hotspot, since WiFi consumes less power than the 3G.