David, I see the conditions you faced where much harder than those I met, but I consider (in my limited knowledge) my experience to be fairly standard for this hike.
I don't mean to underestimate these mountains (or any mountain), right on the contrary, I treat them with the greatest respect and caution to the extent of being a bit of a whimp sometimes. I think you did great from what you describe. It wouldn't have been easy for anybody, surely not for me.
I just wanted to point out this place, as beautiful and rugged as it is, is far from remote. Anybody visiting that expects remotess will probably be deceived. You're never more than a few hours far from a road, at 25 m./day I was crossing a tarmac, well travelled road every day but one (I think) on my whole traverse, there are long road walks (in Andorra and Cerdanya), you go across ski resorts... that doesn't make the trip any easier or the scenery any less dramatic but I think it bears mentioning.
About some of the things that were asked / commented on:
I used trail runners (Vasque Velocity) and carried no crampons but I did carry an ice axe which I never used but was IMO mandatory safety gear if only for the Col Inferieur de Literole. The snow may be hard frozen and it's steep. I went over Literole in the afternoon of a sunny day, the snow was soft on the surface and there was a good track of footprints on the east (steepest) side. Next time I'd use trail runners again but I might take some compatible crampons expecting they'd be dead weight 99%-100% of the time but that 1% may make a difference.
Other than the snow, I found trail runners perfect for the task. I don't recall any significant scree slopes. Talus and Boulder fields are common in a variety of boulder sizes but I actually find trail runners an asset over boots in such terrain.
Fog is indeed a north side thing. It may obviously happen anytime, anywhere if the weather is bad but on the french side it's common to have fog during stable weather conditions. It developes in the valley bottoms during the night (cold air sinking and humidity condensing, I guess) and raises during the afternoons/evenings, covering the high areas where the route goes and may give hikers a hard time route finding in the highest parts where the trail is faint or non-existant but if the weather keeps stable the fog will usually dissipate during the night and the morning will be clear in the high areas.
Fall 08 has been indeed a particularly snowy one all over the Iberian peninsula and the Pyrenees got dumped. We'll see how it goes during the winter.
The usual window in the HRP is July to September. I'm no pyrenean expert but I'd say easiest time is August and September: the steep sections look much friendlier with no snow. Between August and September, it's a hard call... August gets more daylight, warmer temps, more people and more chance of thunderstorms. September is colder but usually stable weather-wise, less people (huge difference here with august), less chance of thunderstorms but more chance of new snow (instead of water) in the almost inevitable bad weather spell. Some services (huts) may be closing in September. Any new snow that might fall should melt out.
I don't know the High Sierra Route so I can't compare. Some HRP passes are steep but I don't think they're particularly difficult for anybody used to scrambling. You'll definitely need to use your hands on the east side of Col de Mulleres but holds are plenty. Just take your time. I didn't find it dangerous or even difficult but I have some rock climbing background. It was dry and completely free of snow when I went through. Wet or snowy would be completely different.
Port de Lavedan south side is steep too but it's basically a walk up and across from the previous pass. East side of Col d'Arrious is steep and on a gully that usually holds late season snow but was almost free every time I've been there. Gourges Blancs has a permanent snowfield but is quite gentle. Literole is sure the trickiest with steep terrain on the west side (at the bottom of the climb, near the hut) and all along the east side and lots of snow in the shadier east side. Anyway, I'd say nothing of this is particularly difficult **if the conditions are favorable**. In the mountains, conditions are everything. I can imagine how tricky it can get in any of those places in wet conditions, not to mention if it's foggy or windy. They're very exposed areas, bad weather feels daunting and can be really dangerous. Waiting the weather is always an option. In the summer, bad weather usually lasts for one or two days but... it's the mountains, anything can happen.
As for languages, I agree french will see more use than spanish.
Comparing trails is difficult. They're all different but the perception we have depends a lot on the conditions met or even such subjective things like our own mood at the time. In general, I'd say the basic difference between Europe and the american west is population density, so much bigger in Europe so trails usually try to take you deep into the mountains over generally rougher ground than they do in America so you get huge, constant climbs and stretches over steep, exposed terrain. There are gentle trails but they're kind of suburban, countryside across villages stuff. On the other hand, civilization is always at hand and it's relieving to know you can resort to it if anything goes wrong. This is obviously a tricky issue in itself as it may affect morale: it may be psychologically difficult to camp in a downpour when you know there's a hut at hand or even a village a couple hours down the hill. In the american west, there's usually no option but relying on yourself, which is again good and bad, I guess I need not explain why. What's more difficult? I couldn't tell.
Camping out in a place lake the Pyrenees is one thing I find particularly tricky, maybe even more than the hiking itself because you're always in very exposed locations for those hours when we're more vulnerable. It's fine (and spectacular) while the weather holds but the weather will never hold for a month straight. That's probably one of the reasons why tarps and UL shelters are not so popular as they are in America as I was commenting recently on another thread. On the HRP, climbing down to camp in the forest is hardly an option, most times it'll mean a big detour and often will take you near a road.
The guidebook is quite enough for planning together with the relevant maps. I have some information about the HRP on my website, most of it is in spanish but that's where most of the pics are (http://www.viajarapie.info/rutas/europa/hrp_intro.htm) but I also wrote some background info in english (http://www.viajarapie.info/routes/europe/hrp.htm). I'm afraid the note at the bottom was just wishful thinking.