I attended the Boston Pops Fireworks Spectacular 3 years in a row, and had similar experiences every year. The Boston Pops Fireworks Spectacular features the Boston Pops Symphony Orchestra, the fireworks on the Charles River, and a featured band which is different every year. Craig Ferguson typically hosts the event, and it is broadcasted on national television from within the Oval in Boston’s Esplanade park.
The Boston Pops Fireworks Spectacular has a pre show on July 3rd (replacing fireworks with confetti) and the main event on July 4th. The July 3rd event is essentially a rehearsal of the July 4th event, so you are really not missing anything by attending one or the other. The July 3rd show has less people and is easier to get into than the July 4th show, but does not have fireworks. I have attended both shows for 3 years.
The Oval is a relatively small grassy area with a direct view of the hatch shell in the Esplanade riverfront park in Boston. In order to get into it for the 4th of July show, you have to wait in line in the early morning hours. If you show up late in the morning, you risk losing a good spot. There are no assigned spots so it is on a first come first serve basis. If you want to get a front row spot, you will have to get in line between 1 am and 2 am the night before, which we did. Otherwise, you will have to wait in line started at 6 am to get a decent spot. Once the oval reaches full capacity, usually early in the afternoon, no more people are allowed in. The Oval is a secure area, and they will issue wristbands so that you can enter and exit the area once you are admitted. Boston Police will check your bags as a security measure and there is no glass allowed. Vending is just outside the Oval.
I have seen people get away with bringing multiple coolers of beverages, so there is no limit to what your party can bring in terms of quantity, but I came in light with just a backpack, a tarp, and a couple camping chairs. Once you are in the Oval, I recommend at least one person in your party maintain your spot, or greedy latecomers will start to invade it. Bring sunscreen, a rain jacket or waterproof tent, because you will be bearing the weather from when the oval opens at 9 am to when the show starts in the evening. The radio is played throughout the day, but I would recommend bringing some form of personal entertainment such as a deck of cards or an mp3 player.
If you want to see the show visually, you must be inside the Oval, because trees surrounding the Oval block the Hatch Shell. However, large speakers are placed throughout the surrounding Esplanade, so you can still enjoy the show if you are outside instead. If you want a good view of the fireworks, I recommend being outside the Oval in the Esplanade on the banks of the Charles River. The fireworks are launched from a barge in the middle of the river. If you are inside the Oval, trees will block your view of the fireworks. I tried exiting the Oval in time for the fireworks, but heavy crowds prevented me from making much progress, and I was stuck viewing them from Storrow Drive. Six lanes of traffic are closed 4th of July to accommodate the exit of the crowds in and around the show on July 4th.
Essentially the Boston Pops Fireworks Spectacular is one big party of 600,000 people in and around the Charles River.