Roman Forum - is it worth the entrance?

I would definitely take the time to see the Roman Forum. I visited Rome in the 70's and the Forum was closed during my stay. I always regretted that I was not able to walk thru it. This last September, I was able to visit the Forum and I was not disappointed. If you will not be on a tour, be sure to read up about it or listen to Rick's audio tour. I think it will be one of the highlights of your stay in Rome. I would also recommend going to the top of the Victor Emmanuel Monument for the best view of Rome.

Jason, the Forum, Palatine AND Colosseum are all on the same entry ticket. You do not have purchase a separate ticket for the Forum (or Palatine). Yes, both the Forum and Palatine are 'worth' it, IMHO, but it's up to you how much time you wish to spend. Just understand that the expense is only in time and not in additional tickets. From the official ticketing website:

http://www.coopculture.it/en/colosseo-e-shop.cfm

"Combined ticket colosseum roman forum and palatine, valid for 2 days, the ticket can be used within 31th december 2016"

On one ticket you may do all three sites on the same day, or the Colosseum one one day and Forum/Palatine on the next. Or the other way around. The 2 days just have to be consecutive, and you have to do the Forum and Palatine on the same day.

Kathy with the combined ticket for all three, if I read the site correctly, you cannot do the underground and third tier of the Colosseum, which is why I was planning to purchase the Colosseum ticket separately.

As yosemite1 says above, the key is to have read up ahead of time well, or to have a good guide there with you. These sites are worth the concentrated attention of generations of scholars who have devoted their working lives to unpacking the history of Rome, so it is definitely worth your time. Like anything, if you bring your informed attention to bear, it gives rich dividends; if you stroll through with your next gelato on your mind, all you'll see is selfie sticks and old stones.

I think I see my confusion: you have to buy the ticket and the tour separately. So if I want to see the Colosseum, I have to buy the ticket for the Forum anyway.

We were there in December 2012 using Roma Passes, and purchased our Colosseum Underground/Upper level tour as an add-on once we got thru the entrance gate. Maybe some of the offerings, procedures and policies have changed in the past 3 years. San Clemente was a pretty easy walk from the Colosseum, and definitely worth the visit (and the relatively small entrance fee to go below the church).

Visiting the Palatine Hill/Forum the next day involved a lot of walking, ascending and descending. The Forum was interesting, and afforded the chance to enter the old Senate building (Curia) and see arches and columns up close. Ceasar's pyre site was really just a pile of dirt. The Forum is a one way dead-end, and you backtrack all the way back to the entrance, unless you use the exit-only gate by the Curia.

The following day, we picnicked on take-away tavola calda pizza for lunch, overlooking the Forum from a panoramic platform above it, but below the Capitoline Hill and Musuem. Definitely go up the Capitoline Hill to see Michaelangelo's square, even if you don't tour the museums, the head down the lane past the Romulus/Remus/She-wolf statue to reach the free Forum overlook.

Ostia Antica was a very worthwhile visit on our last day, too - a must.

If you're a fan of the Mithraic mysteries (who isn't?) and the other dying-and-rising god cults of the Mediterranean, then Ostia Antica is like heaven. Be sure to read David Ulansey's book beforehand, though.
http://www.amazon.com/Origins-Mithraic-Mysteries-Cosmology-Salvation/dp/0195067886/ref=sr_1_1?s=books&ie=UTF8&qid=1460259904&sr=1-1&keywords=ulansey

I think I see my confusion: you have to buy the ticket and the tour
separately. So if I want to see the Colosseum, I have to buy the
ticket for the Forum anyway.

Yes, you have to purchase the general entry ticket for all three sites in addition to one for the Underground/third ring tour.

We were there in December 2012 using Roma Passes, and purchased our
Colosseum Underground/Upper level tour as an add-on once we got thru
the entrance gate.

This tour is selling out in advance very, very quickly these days. Other than maybe low season - and even that is risky - I would not bank on being able to get tickets as a walk-in if it's on the must-do list.