BradJ:
I will state again that I believe DIR isn't necessarily suited to providing the average recreational diver with the appropriate course of continuing education.
This invites a response like "you're entitled to your own opinion". And you are. And in fact, I agree that an 'average recreational diver', whatever that means, may never want to take Cave or Tech 1, so their only GUE course will be DIR-F, though they might want to take Rec-Triox, which I think is probably going to become increasingly popular as divers realize that diving Helium is much more fun than diving air.
In my experience, I almost quit diving
before I took DIR-F, and that course was the only reason I stayed in the water. DIR-F is where I actually learned to dive. The skills I learned also enhanced my pleasure in diving by an unmeasurable amount. Diving is much more fun for me as a DIR diver because of the buddy relationship and all the cool things that I couldn't even imagine being able to do before.
But to respond to the original topic of this thread, I think there can be disadvantages to diving DIR, and you have to choose to accept them and not have them interfere. I think these have already been mentioned by other people on this thread, so my apologies for repeating them.
1.
If you've already been diving awhile, you will probably have to buy some new gear. I was lucky; I hadn't bought all my gear yet before I took DIR-F, so I only had to buy it once. And let's say you buy a 10W canister light, and then the first time you dive with a buddy who has an 18W, you're going to want to upgrade. And then if you continue your GUE education, you're going to be tempted by ridiculously expensive things like Gavin scooters and Halcyon rebreathers and personal fill stations with a compressor and booster and Helium and Oxygen. So the initial gear purchase or changeover might be expensive, and any new toys you want after that, are ALOT more expensive.
After your initial gear purchase, though, I do believe that you save money in the long run, if you stay in recreational diving, because you don't need to buy any major new gear and you'll never be tempted by the latest stupid gadget at DEMA.
2.
You might have trouble finding DIR dive buddies and limiting yourself to not diving with non-DIR divers. I don't see this as a disadvantage, but I live in DIR mecca, so I have never had a problem finding a dive buddy.
3.
When you dive DIR, you move around alot less, and in cold water, you get colder. I'm being serious; I have hadalot of problems with staying warm, and diving DIR immediately reduced my energy output and made it harder to stay warm.
Those are the only things I can think of, offhand. The benefits far outweigh the disadvantages, in my experience.