Andy, it is definitely worth doing. I think I've done it about seven times now - albeit not for the last couple of years - the sheer numbers are something I appear to be shying away from, but that shouldn't put you off.
What's your weekly mileage? Assuming you ride regularly, the old wives tale / folklore / feng-bikey has it that whatever you ride in a week, you should be able to complete in one hit without undue stress. Assuming you ride regularly.....
If you don't, you'd probably benefit from some rides to build up the miles in your legs. Just so you can enjoy the ride - rather than find it torture....
Tips:
- Take food. Take all the food you think you are going to need. Although in recent years there have been an increasing number of pop-up entrepreneurial bacon roll vendors in the second half of the ride, the main, official, half-way food stop is not to be relied on - they can easily run out of food if the weather forecast and turnout is good. Depending on when you arrive at Dunwich beach, the queue for a full English at the Flora Tea Rooms could be > 400+ strong. Other breakfast options (The Ship) are available, but are very thin on the ground, and easily over-subscribed.
- As has been said, take a couple of tubes, and some tools to fit them with. Check, or have the bike checked over by someone who knows which end of a screwdriver is the end you hold, before the ride. There's a camaraderie on the ride which suggests you needn't take the entire contents of your Parktool tool box with you. Figure out if your bike has an Achilles heel, get that fixed, and pack tools accordingly.
- The return journey. Some cycle back, I never have. www.southwark.cyclists.org have for many years organised return coaches, with your bike travelling with others in one of several lorries. It's an option which plenty go for - I think the numbers repatriated thusly last year were 800+. If you can live with their timetable, and aren't retentively precious about the paintwork on your frame, then it is one solution. The last couple of times I've done the ride, once I'd reached Dunwich I've ridden solo to Diss, to catch train back to LST, a further 26 or so miles, along some lovely, traffic free lanes. It's a nice contrast to having spent the night on the road with 1,000 road warriors. Prior to that, and my top tip to you, is persuade someone dear to you, to come and collect you by car. I had the added and unexpected advantage that my chauffeuse elected to bring with her delights like bouquets of flowers, bubbles, chocolate & a blanket. It's a struggle to decide which is the better option for me - the VW Passat estate and bubbles, or the the 26 solo miles to Diss.... On your first Dynamo I'd go for the former if I were you.
Do it.
I did it because (in about 2006) I stumbled across it on the interwebs (It is the one single factor that made me buy a bike and return to cycling), and thought 'I must do this, before it becomes too big, too organised, and someone says "Risk Assessment / Method Statement / Entry fee / Conditions / Etc; Etc"
Unsurprisingly that's the way it looks to be heading.
Do it.
Enjoy it, it is not a race.
Go suitably equipped.
Don't let the twattishness (inevitably, there will be some) of some of the riders spoil your night.
Do it.
And then look forward cadging a ride on any battery-powered (small turn-out / different dates) versions which are offered on here - for a wholly different experience.
I hope you choose well, Andy, and enjoy it when you do.
J
ETA
There's an uncommonly sexy full moon out there tonight.
If your ride has one of those, you'll definitely be in Happy Street.
You'll note that Steve's campervan plays a part, it was fledgling CC adventures (with snazzy shirts etc) 
