I also have the current Henry ("002") version of the AR-7. While I like it a lot and find it accurate at relatively close ranges, like all survival rifles it is a set of compromises. The (original) AR-7 also has the distinction of being used by James Bond in a couple of movies.
The Henry is the only AR-7 version currently in production. The upside of the Henry version of the Ar-7 is that the Henry has several improvements over the previous versions (Charter Arms, etc): an additional magazine can be stored in the stock, the stock seals better against water, the stock is made of a more resilient plastic, and there is an accessory rail integrated into the receiver. The rifle floats both when taken down (receiver & barrel stored in stock) and when assembled. Henry has also tried to make it corrosion resistant (better be if it is intended to survive water adventures!).
The downside is related to the AR-7 design rather than the Henry version: the stock is wider than normal and a bit offset, there is no forward grip (forearm, etc), and the magazines are touchy. Attaching accessories to the barrel that may put lateral pressure on it (ie, sling mount, forward grip, etc) risks bending it.
There has been a lot of discussion about the comparative build quality of the various manufacturer versions of the AR-7, and I don't know that there is complete agreement. Issues center on reliability and the quality of the barrel. My take is that, in general, users seem to think the original AR version was the best, the Charter Arms version the worst, and the Henry version is a distinct improvement over the Charter Arms version and approaches the AR version in build quality. There are also some other variants out there (such as the version used by the Israeli Air Force), but most are too uncommon for people to have had much experience with them.
Another rifle to consider is the Savage/Stevens model 24 (many versions over the years), an over-under rifle/shotgun combo, most commonly found in .22LR/.410ga, but also in various combinations of .22 Hornet, .22WMR, 20ga, and 16ga, and I think more. This is a takedown rifle, but obviously heavier than the AR-7 (wood stock), doesn't float, etc. It is also a single shot rather than a semi-automatic.
The Savage/Stevens model 30 is another contender. This is a take-down lever action .22LR or .17 rifle with a wood stock.
And yet another rifle is the Springfield M6 Scout (various manufacturers, including Springfield Armory and CZ) -- another over/under combo, usually .22LR or .22 Hornet & .410ga. Like the AR-7, this was originally a USAF survival rifle; in fact, it was the rifle the AR-7 replaced. It is all metal, folds in half (in original military configuration, or if the triggerguard is removed from the commercial configuration; otherwise it folds into a "V"), and stores some rifle & shotgun rounds in the stock. It will not float, and is significantly heavier than the AR-7. Like the Savage model 24, it is a single shot.
Of these three, the least expensive is the Henry. Savage 24 prices vary considerably with the age, configuration and condition (these have been made since the 1930s or 40s), but generally start at $250-$300 for working used examples. The M6 Scout is no longer being made and has become very popular the last few years -- prices generally start at about $500-600.
Considerations when deciding what kind of rifle is best for you include the environment you anticipate using it in (ability to float is less important in high desert or mountains, for example), weight, durability, size (when taken down), the relative merit of a small gauge shotgun vs a .22 for hunting small game, whether you need a scope, and, of course, price. A survival rifle is not likely to be a safe queen, so over time you can expect it to end up knocked around a bit (in your backpack, car trunk, truck, boat, airplane -- whatever).
If you Google "survival rifle" you will get a lot of hits. You might find these articles helpful starting points (and information on more rifles):
http://www.airaffair.com/Library/Archive/Part2/survival_guns_for_aircraft
http://www.chuckhawks.com/survival_rifles.htm
http://www.survivalboards.com/2010-10-10/top-5-survival-rifles/
Bill
.22lr Survival rifle
) Reliable, and lighter. If you want it to float, tie it to your cooler. 
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