Yes I would say that it is well worth it. The 2 sims are installed into a single razorworks directory, C-H has the latest A-H patch. First you install A-H, patch it and run it once. Install C-H and then go to http://www.simhq.com/ Go to the combat helo section and you will find a nice utility by Flexman that will remove un-needed files from the A-H install and it lets you do some other very cool stuff.
Now you have both ready to fly and here is what you will find. After the campaign screen you will be asked to choose a helo, this is really only asking you what side you want to fly for. Once in the game you get to choose what helo for that side you want to fly in based on what helo is assigned to the mission you want to take. So you now have A,C-H,H as a sim.
In C-H you will get 3 new campaigns and all 3 of the old A-H ones plus some new games called skirmishs. These are just mini campaigns in the C-H theaters. For all of the old A-H campaigns you get all the new AI and wingman control, the new campaign system and some improved graphics. There is also some better FMs for both the old helos..
I am sure I am missing stuff but isn't that enough? The two sims just become one with all the new fixes. It is an amazing setup that Razorworks have put together.