I heartily concur with Trailrunner w.r.t. searching existing threads, but thought I'd give another perspective since I carried a Solio with me for most of my PCT thru-hike this year. I don't agree that it's only useful in a "slow, leisurely jaunt" type of hike. I tied mine on top of my pack and it helped a lot to augment the opportunities to recharge my smartphone from wall current in towns --- particularly in sunny California. From northern Oregon through Washington, it will be less useful, as the sun is less directly overhead and there's a lot more tree cover. In fact, there's lots of tree cover in places in NorCal and southern Oregon too, but I still found it worth the weight and hassle there. I think I finally ditched it at the OR/WA border. I saw a few other hikers carrying on of these on the trail and I met one thru-hiker in Washington state last year who still had his Solio with him and was using it, so YMMV there too.

One '08 thru-hiker of my acquantaince (Flippy) used a GoLite umbrella and replaced the tip of the umbrella with a little rod that his Solio slipped firmly on to --- so he could recharge when the umbrella was open, or when it was closed and strapped vertically onto his pack. I didn't find an Umbrella to be worth carrying, so I tied mine on, but since a thru-hiker spends most of his or her time on the move, it is indeed IMO important to attach it to the top of the pack somehow if you're going to bother to carry one.