depends on your house's setup.. if it's all concrete and metal in the walls, then it's not going to go that far.
Generally you don't get too much data loss, but that depends if you have alot of RFI Radio Frequency Interference around. Things like strong 2.4GHz cordless phones right beside the WAP or a client, or anything that would have a strong radio broadcast.
Security is one problem.. it's not usually a big problem, but it may allow your neighbors, or someone walking by, to connect to your network and look around, or use your internet connection.
You can game on it, but it may be a bit slower than ethernet.
Wireless is generally 11Mbits. If at all possible, i would recommend a wired network, that would speed up your network to 100Mbits (or even 1Gbits).
If there's a problem with using a wired network, then maybe it's a good idea to create a hybrid network. Basically get a router with wired capabilities and put the most computers possible on the cat5 and the rest on wireless.
The only problem you'll see is that the connection will be slower on the wireless systems because it's highly recommended to actuvate encryption on the wireless bands. It'll reduce speeds, but it's worth it if you'd like to protect your stuff and not have everybody in the neighborhood with a wireless laptop use your network.
Hope it helps, pal! That's my piece. Just say the word for more info.