The Xera's are great. They're very compact and well made, and work great as a helmet spot. I run two on my helmet, with a y-cable to a 4-cell Gemini battery. Their battery has kept its charge through 2 full seasons, with no detectable change in the ability to hold charge (Can't say the same for the Magicshine batteries). I angle one slightly farther forward of the other, and use them for spotting the trail ahead of me, which is particularly helpful when I'm moving fast. I have a separate bar set-up that is more flood oriented. I just pop the battery in the back jersey pocket and run the wire up my back. Works great.
I picked up a SolarStorm as a back-up from Lightmalls. Yes, the 5000 lumen claim is simply ludicrous. I would estimate them at 600-800 maximum based on direct comparison with Light and Motion units that I know to be accurate. The battery does beg for some waterproofing, and I will add some silicon to the backplate. However, for under $45 delivered, I'm pretty impressed. I still prefer proven quality units for my primary lights, as I like to do 2-3 hour solos. However, the SolarStorms do provide a very accessible entry-point.
Most helpful thing I came across so far, is to buy a schwack of assorted length velcro bands from Ebay. I think I payed under $10 (delivered) for a bunch of blue straps ranging from 6" to 18". These are dynamite for keeping batteries in place if you use a bar-mounted light with remote battery. Also fantastic for mounting smaller battery packs to your helmet. They also can be used for pumps, tires, and other things. I always keep a spare with me when I head out at night in case I need to bojangle my setup.