To answer the original question- no. I don't think the Fig 8 is worth carrying aloft for the potential self rescue. When I hear "rescue" I hear "I'm probably never going to need this...but just in case..."

To use a Fig 8, you need a carabiner. Leave the 8 and use a munter. All you need is the 'biner! See a reference to rec tree climbing and this hitch here: http://en.wikipedia.org/wiki/Munter_hitch

The only aspect the 8 beats the munter is that the rope twists a LITTLE less that the Munter. If I was concerned about twist, I'd carry a Rack.

love
nick

IMO for rec climbing there are too many better options.

I carry a figure 8 with me when working in trees. When in pines or other trees with a main spar I like to choke my climbing line via 'biner or simple bowline to the spar then run the single line through my figure 8. This is my secondary safety. If I ever need to get out of a tree quick, like for bees, I can un hitch my primary safety (steel core flip line) and drop quick. It also comes in handy some times for self rigging static loads or light limb drops.

I'm only a novice tree climber, but I've been a rope rescue technician for many years. I guess I did things backwards, but my first experiences with tree climbing were SRT-type. (I think that's right - Someone correct me if I'm wrong) I tie an anchor at ground level, climb using ascenders and then switch over to decender to come down. At least that's how I did it. There's definately more to think about, more gear to haul, handle(and drop),and unless you use a prussik loop as a self belay, I think there is a greater safety risk for a novice using an 8.

I use a rescue 8 all the time, because that's what I'm familiar with. I'm learning different methods now, so I can see why some people either love 8s or hate them. I carry mine because it can be used as a rappel device, belay/lowering device, and a rigging plate.

As for the weight. My Kong 8 (alum.)weighs only a couple of ounces. I do have a stainless steel piece that is QUITE HEAVY - but it's rated at over 11,000 lbf!

IMO, use what you are comfortable with, but it never hurts to learn alternative methods - I am.