Ever since I started networking between 2 computers on my home network back in 2001, there were always annoyances with not being able to see the other computer, etc., but none were as annoying as when Microsoft first released Windows XP Service Pack 2 with a built in firewall. Don't get me wrong, the firewall was desperately needed. Previous to me being network savvy, I ran my computer like many other college students, open to the Internet. For most people this wasn't an issue because they were only on their computer over dial-up, but I had access to always ON high speed Internet since 1997. Windows XP SP2 made me feel better about my mother and my in-laws having high speed Internet access without using a router with Network Address Translation.
I have always felt pretty secure connected to my router that uses NAT and has an SPI firewall. Not only that, but all of my PCs have NOD32 antivirus and I stay away from porn and "cracked" software. So when the Windows firewall started causing me annoyances, I just disabled it and have done so ever since.
Now I am running a domain controller with two client machines (hopefully it will be three soon), two network printers, a network scanner, a media center that streams video from the server, a couple work laptops, a couple sandbox machines, and 4 or 5 other guest machines depending on what family members or friends need my help. Would it be worth it to try and enable Windows firewall and work with it to get that extra security? Let me know what you think.