There isn't much different in terms of singlehanding a boat, whether it has one, two, or three hulls. However, what you learned on Aquacats and Hobies is going to be very different from what you'd experience on a cruising sized multihull. Beach catamarans are relatively overpowered and really won't teach you much about handling a cruising sized catamaran.
First thing I'd recommend is that you read the following books:
- Chris White's The Cruising Multihull
- Thomas Firth Jones's Multihull Voyaging
- Mike Mullen's Multihull Seamanship
as a basic foundation of knowledge about cruising multihulls.
One of the big problems for monohullers moving over to multihulls is that some of your reactions are going to be wrong for sailing a multihull safely. Also, the speed of a multi-hull means that things can go from safe to dangerous very quickly, unless you really understand what is going on. This is especially true on large catamarans, which tend to not give as much warning when they're at the point of getting into trouble.
That said, most of the problems I've seen on multihulls, is usually human error. The biggest problem that I see with new multihull sailors is that they get so taken by how fast a multihull can go, they don't seem to realize that you shouldn't really sail one as fast as possible once conditions start to pick up. It is very difficult to capsize a cruising size multihull that is properly sailed—however, it is very easy to capsize one that is improperly sailed.
Think of a multihull as a sports car.... yes, they can do 120 MPH... but that doesn't mean that it is wise or prudent to do so all the time. For example, while it is probably reasonably safe to drive 120 MPH on a closed, private sports track that is dry and well maintained—it probably isn't as wise to do so on a wet, pot-hole ridden, icy city street in rush hour traffic.
Also, in strong winds and heavier seas, dropping the speed of the boat down a bit makes the ride for the crew much more comfortable, and reduces the risks of pitchpoling and capsize drastically.
I've taken my boat out in conditions that a lot of other boats wouldn't consider going out in, but I haven't had a problem, because I know the limits of my boat, and don't push it in those conditions.
There have been a few stories recently of Corsair trimarans capsizing—most recently, what looks like a Corsair 31 off the coast of New Jersey, on its way back to New England. The Corsairs are significantly lighter than my boat, with more sail area... and also, IIRC, have smaller amas, that are higher off the water. I believe the difference in sail area, displacement, and design contribute to the reasons why the Corsairs have capsized recently.
I also believe that the attitude of the sailors aboard the boat may contribute to the risk of capsize—if the sailors have a racing mentality and are used to flying a hull and pushing the envelope... I think they're far more likely to capsize the boat than a boat with a conservative cruising mentality crew.
Catamarans will have the most living space and stowage space out of the three types of boats—mono, cat, tri. They will also often have the worst sailing performance of the three, due to the high windage, high freeboard, low bridgedeck clearance and small sail plan that seems to be fairly common on many charter-market catamarans. Non-charter catamarans seem to have some better sailing characteristics in some cases.
Some catamarans can have problems in light air, due to the wetted surface area presented by having two hulls in the water. In heavier winds, they can have problems tacking or coming about due to the windage caused by the bridgedeck and cabintop. This is due to the designers need to make the boats exceptionally spacious and roomy as desired by the charter market.
Trimarans, especially the more modern designs, that eschew the full wing deck design that was popular in the earlier designs, will have the least amount of living space and stowage space. They will also tend to be more weight sensitive than a catamaran. There are exceptions to this of course, like the big, full wingdeck trimarans that you sometimes see in the charter trade, with 8+ berths, etc.
Trimarans tend to do a bit better than catamarans, in terms of sailing ability, since they tend to pivot on the center hull, which a catamaran can't do, and have less wetted area, since the amas are much smaller than the main hull. This is especially true on the performance oriented trimarans, which are usually designed to have only one of the two amas in the water at any time.
A lot of the rules for monohulls don't really apply to multihulls. For instance, the scantlings for monohulls are often much, much heavier than what you'd find on a similar LOA catamaran or trimaran. This is due to the fact that catamarans and trimarans don't have to support the weight and mass of a heavy metal keel.