I just ordered the Hypermac Mini for $59 (including shipping). The cost was a factor as it's $37 less expensive than the Solo, but even on sale it's not much cheaper than the Newtrent IMP880 or IMP1000. However, Hypermac have a very good reputation as they've made backup batteries for Mac laptops for a while and the Hypermac Mini has the best form factor; it's only 0.5" thick and can slip into a pocket or bag easily, the others are far more brick like, although not that much heavier. It also allows pass-thru charging so you can charge it and your iPhone at the same time, the Solo doesn't and I'm not sure about the Newtrent models. The Hypermac also looks really cool ;-). Finally it's interesting to note that Hypermac Mini claim to recharge an iPhone (not sure which model) 6 times and Newtrent claim 5x for the IMP880 and 6x for the IMP1000 even with their larger batteries. This may be them just being conservative or Hypermac being optimistic, or it might be because of the grade of batteries used.