I found it to be useful in my rec diving for several reasons:
- Having training that exceeds the requirements of the dives you're doing gives you a set of skills/tools that will allow you to manage more complex problems than you are likely to encounter on a recreational dive. That helps to make you a safer, more knowledgable, and more skillful diver.
- The Adv. Nitrox class gives you more flexibility with regard to how you chose to execute dives within your current range. A deco dive doesn't necessarily mean going deeper... it can also mean staying longer. Instead of two bounce dives to a 120' wreck, you could (if you wanted to) go down, stay a while, and do a short deco. Instead of just seeing something deep, you could hang out and enjoy/explore it. So long as you know how and do the required planning, it's nice to kiss the NDL goodbye.
- You'll learn to plan and manage your gasses properly, and that's good for any diver.
- You'll learn to dive with greater task loading, which will make future recreational dives that don't require so much planning/attention to detail that much more enjoyable.
- Since there's really no such thing as a no-deco dive, the more you know about planned deco, the more you understand about diving in general.
- You'll probably have a lot of fun.
That said, I took IANTD adv.nitrox and rec. trimix, and I've never even considered taking deep air. I still don't have any particular desire to do so. If you have experience diving past 100', I personally wouldn't bother with it.
