I absolutely LOVE my LP85s. The HP 80's can be problematic, because they're really short tanks, so they tend to put you head-heavy (which is an inherent problem with doubles anyway). The LP 85s are longer, and the first time I put them on, I sighed with pleasure at how easily I could balance them.
They're the most tank I can move around doubled up, as far as picking them up and putting them in the car and such-like. I think you'll be surprised, actually, at how easy doubles are to wear and walk around in, although your butt muscles get tired if you have to climb hills in them.
The biggest issues in transitioning to doubles, I think, are these two: One is trimming out the rig so you aren't an obligatory head-first lawn dart. I started with a set of LP72s (which are decent starter doubles, too) and I had to fiddle for a long time with gear to try to balance them correctly. I switched from a SS to an Al backplate and put the extra 5 lbs on my belt, and even went so far as to put 2 one pound weights in my drysuit undergarment pocket, which got me close to balanced. The LP85s, on the other hand, with the Al backplate and 16 lbs on a belt, balance perfectly.
The other challenge is to develop proficiency with valve shutdowns. There is no point in diving doubles if you can't manage your manifold. Then you've just added a whole bunch of o-rings (failure points) without getting anything in return except carrying a bunch of weight and gas you might lose. Learning to do facile, smooth valve shutdowns without losing buoyancy and trim takes time, and sometimes gear changes. People often find that their dry suit or undergarment is too restrictive to permit reaching the valves, which is an expensive insight. Others need to do stretches to achieve the shoulder mobility to get back there. And most people take time and practice.
I have actually gotten to the point where I way prefer diving my doubles. They're more stable in the water, and give me tons of feedback on my position. It's easier to control buoyancy because they have so much inertia. (Which means they're reluctant to leave where you are, but once they get going, they're equally hard to stop!) I like putting them on the boat and not having to swap out tanks on a 2 dive day. And the knowledge of the extra gas is nice on deeper dives.
Girldiverllc and I are going to put on a "girl's doubles day" in August, and try to encourage a bunch of women to show up and give it a try.