Also received mine today. Agree with all the comments above. Does make the phone twice as thick & twice as heavy. Strange that the instruction booklet shows a diagram with the charging port half way down on the right, but it is actually at the top on the left ( where the hump is ) !. Still need a screen protector as there is no lip at the front, but camera lens wont get damaged as its deeply recessed. Does not effect pics or videos though. Also noticed that it will only fit with the original battery cover, if using one of those cheap replacement covers the bottom section will not click into place.
Overall I think that at this price its ok, certainly not worth double. If you want to be sure your phone will last the whole day or perhaps a weekend, & dont want the hassle of carrying a spare & removing & replacing the back cover, then this will be very usefull.