So I' m just getting moved into a new apartment, and there' s an open wifi connection here. I' m thinking of getting a wireless adapter for my Xbox, but I' m wondering if the connection here is fast enough. What' s a good connection speed to avoid lagging out all the time?

Wireless speeds really depends on many different variables. In an ideal real world situation, you' re lucky to get half of the 54mb/s that 802.11g supports. This speed can be further reduced by:

Building materials
Other wireless networks (" unfriendly neighbour" devices. MIMO is a bandwidth hog)
Other devices that operate on the 2.4ghz range (cordless phones for example)
Electromagnetic interferance

It really does depend on what' s around you. There' s no set answer. But i' d say at least 512kb/128kb connection speed but more would be ideal.

Wireless is pretty crappy for gaming in all honesty. People using wireless are worst off then people sharing their connection. You' re much more likely to lag in a match and can even drop the connection entirely (in some cases this is frequent). Forget about hosting.

My 360 is wireless and checking the connection settings it' s usually at almost full (checking the bars on the network settings screen all the bars are usually full apart from the last one); I' ve noticed little in the way of problems or lag playing online. The only problem I have is people turning on my PC without me knowing basically taking all the bandwidth and knocking me offline.

How do people turn on you PC without you noticing? Is it like miles away from you?