If the components to the award are something which interest you (walking, skills, volunteering) I'd give it a go; it's one of the those time bounded opportunities that you can only do when young, so if they're the sort of things that might appeal to you, definitely jump in.
Regarding the CV building aspect, which should be considered secondary imo; as much as the award itself is a tick mark / achievement, the activities contained within give a candidate something attractive to talk about at interviews, or even just networking. Having worked at a university career service, a couple of key skills top employers asked for in graduates were 'knowing your own strengths and weaknesses' and 'the ability to plan and follow through with it / make it happen'. Granted not everyone wants to go down that route / play that game, but at the very least the DoE gives experiences that can be interesting to hear about in an interview - give the candidate more depth than 'in this module / class I found' ... Second to that, as a mature student I recently returned to full-time higher education. Mixing with a lot of solid students (AAAB etc) the DoE just seems to be something that an awful lot of people have done as part of their outside of school activities - so if a person is going down that route, it's something they probably want to have to be competitive.
Getting back on track, personally, like I said above, if the activities therein interest you, I'd crack on. I had a great time as part of St John Ambulance during my DoE volunteering, and alongside this learnt some interesting bits and pieces as part of the skills and activities portions. Made some good mates etc. Like I say, it might be that you're already doing this, but to me it was just a chance to formalise it and get some 'academic credit' for what I was already doing.
With regard the exped, and "knowing more about maps than the qualified leader" - again, I'd crack on. In most of the jobs I've had, at some point, I've encountered 'specialists' / qualified folk than whom I'm more knowledgeable. At the same time, providing they're capable, it's an opportunity for you to maybe help out those in the group who are less capable (again, something to talk about at interview, or just feel good about), or pick up bits of knowledge that the instructor might know better.
You ask, "is the DoE Award a good experience?" - Like I say, other than the exped, you can pretty much make the rest of the DoE experience what you want so to me it makes sense to kind of get credit for something you really enjoy doing. Filling in the wee health and safety things and the nominal charges is a bit annoying, but on the whole it seems like a small price to pay for what you'll get out of it. Obviously you could have an expedition that sucks due to circumstances beyond your control, but to be honest, some of my hill memories I look back on most fondly are the ones that absolutely sucked at the time. For what it's worth, it sounds like you (OP) have enough knowledge and skill that you can mitigate the chances of that happening.
The DoE award is good for employability, but at the end of the day, it's more about the experiences of which it is comprised. Like I say, these are available for a limited time, and I for one am glad to have taken them as I'm now too old to go back and do it.