The P100 is probably the best case for my Vita I've ever had (I had 3 before it). You can tell that it's made specifically for it. The outer shell looks soft, but is MUCH harder than it looks! When I opened it, I was a little concerned that the tray didn't have any padding to hold it, but after putting my Vita in, I realized that it doesn't need it. It fits the slim Vita perfectly, as long as it doesn't have a big plastic protective case (I don't mean a screen protector), and holds it snugly so it can't rattle around. The strap that goes underneath the system and out the top makes it very easy to remove it. Also, the tray that holds the Vita is slightly recessed, and with the soft flap above it, prevents the L&R sticks from being damaged. Plus, this model has 10 pockets on the flap that tightly hold games (only one in each) and any extra memory cards.
The little zipper pocket is big enough to hold a charger and anything else you need. Personally, I use my phone charger for pretty much everything, but I still keep a USB cord in there just in case.
My only complaint is with the pockets. The material on them is a very thin mesh cloth, and therefore feels kind of flimsy, and seems like they will eventually tear (maybe it's just the case I received), but it's definitely not a deal breaker.
All in all, I highly recommend this for anyone with a slim Vita! Just make sure you don't get the larger version (the P100L) if you don't have a protective plastic case. That one will NOT hold your system tight, and has enough room for it to rattle around (I originally got that one, so I learned from experience, and returned it).