Hey Sven Glock - Thanks so much for the helpful feedback!
For items 1 and 2 I just forgot about them, to be honest. 
I was rushing a little bit and, since I do this in my spare time, sometimes I forget where I left off or what I was working on. I'll put these back in since they're both pretty important to people.
Item 3 is covered in the "Information Only" option with the "-D" switch. This will show you all the interfaces you can run tcpdump on.
Item 4 I like the idea of "On/Off" and then maybe have a little item about printing to the screen versus saving to a file. I'll update this as well when I'm putting back the additional "Save to File" options.
For item 5, have you never seen a MAC address with 11:11:11:11:11:11:11:11:!1:$" before? 
Seriously though, those checks are currently in the works on my laptop - I just haven't pushed them to the public site yet. As for the "host" filter, as goofy as this sounds, it's possible that someone has "11111asdfasdf" as a hostname somewhere. I will be putting in some "guessing" checks for those but it's almost impossible to know what people can put in for those types of filter. For example, the following three items are all valid: 1.2.3.4, 2001:bad:c0de::1 and 1.2.3.4.com (IPv4, IPv6, host/domain name). I will be testing out some RegEx to see if I can get it to work properly but I may be left with just guessing. Stay tuned, though.
Item 6 is a bit more involved... You see, HTML select and option elements are not able to be styled by CSS as some other HTML DOM elements. The same thing goes for radio buttons and checkboxes. To be able to create a bold section title or have custom radio buttons (for example) would require a fair bit of coding since you have to hide the existing HTML <option> element, create new HTML/CSS for the custom look and then have a JavaScript caller to handle the events. But... And I'm not joking about this... While writing this out, you did give me an idea that may work. Instead of using an HTML select/option combination, I could create an HTML/CSS menu instead and use an onClick function on the spans to call the back-end JS. I'm going to try this out to see how easy it is to get working. Thanks for helping me think of a new (possible) solution, Sven.
I like the idea in item 7 about shortening the list by using radio buttons for src/dst. I will also try merging the host/net option by looking for the "/" character but I may keep host and net separate to make things a bit easier for new people. But I will give it a try and see how it goes.
For the last item, it's a good idea in theory but, personally, I think it may not work as well in practice. Here's what I'm thinking... We know that there are many useful combinations of TCP flags like SA or FA or even the old XMas tree scan with FPU set. But people who are new to PCaps, TCP or networking in general may not. By keeping the filters separate, the users will learn that the flags are unique per filter which, in turn, will help them learn that each TCP flag is unique and then they have that extra knowledge. The other thing is newer people may get confused if they have to create logic gates with this type of filter and they may be tempted to put checkmarks in boxes that already exist when, instead, they should be creating a new filter inside their logic gates. But maybe I'm overthinking this.
In terms of my weekend... I'm currently fighting a sinus cold (yay Canadian weather!) so between that, family obligations and getting drunk on cold medicine, I'll see how much time I've got for this. Maybe I'll work on it after taking some cough syrup and see if it makes my code better or not... If the next dev push has a bunch of cat pictures instead of usable code, you'll know why.
