And of course, if you can see the traffic, you can spoof the same User-Agent as well.

Plus, your source IP can change from request to request when your ISP transparently pushes you through one of many proxy servers. AOL does (or did) this, as do some large European ISPs whose names escape me.

Yet another reason NAT sucks...

I realize that but at least my neighbors won't be able to hijack my session from home. Logging in over a public network always seems risky.

Are your neighbours on your private network? If not, you don't need to worry about them capturing your network data, because they're not on the same network.