Used if for the following so far:
- Rubber gasket for air compressor
- Plunger O-Ring
- Vacuum cleaner belt (Oreck vacuum; It only lasted for a few hours, but that's pretty damn good for not having any thread lining)
- Transmission cover for motor cycle (exposes material to oils, moderate heat, and fuel fumes)
- Pellet gun seal (Constantly coated in oil)
- Bicycle Grip
- Door stop bumpers

So far I've come to these observations:
- Very resistant to oils and moderate corrosives
- Doesn't like glues or cements (If anyone finds a good bonding agent for this material please respond to this or PM me)
- Very strong layer bonds
- Good flexibility and shape return after flexing

I do a short review of the 'Flex EcoPLA' material HERE: goc3d.blogspot.com/2014/11/3d-printing-filament-basic-review.html

I have some tips on keeping it adhered to the bed HERE: goc3d.blogspot.com/2014/11/3d-printing-tips-strength-accuracy.html

*FYI; 'Flex EcoPLA' in not a PLA material, its actually a TPC (Thermoplastic Co-Polyester)

Bumping to see if any more progress has been made in the way of flexible filaments. IronMan stated he would give an update.

Sorry, I didn't know anyone was waiting for an update...but here is a recap of what I've done to run the EcoFlex Black:

After countless misfeeds/coiling up of the filament above the extruder and six failed prints, I finally got it dialed in.  The stuff is not very rigid and will not feed well into the heater core unless the temp is just right, otherwise, it will corkscrew:
- Adjust all print speeds to no more than 10mm/s
- Extruder temp setting in RH and Slic3r at 185c - or Hotend temp at 210-215c
- Print on glass with no hairspray
- 6mm brim
- Bed Temp at 45-50c
- Filament feed into the extruder directly from above; it will bind if trying to feed through any guides

The next most important issue is the print speed.  I was running 10mm/sec on the first layer which printed just fine, and then forgot to adjust the speed to 10 on the subsequent layers.  They were set to 30mm/sec and it started to buckle immediately.  Make it 10mm across the board (except for travel=130mm/sec) and it should work fine.

One more thing; back off the tension on the idler to where it just holds securely.  Too much tension riddles the Flex PLA with teeth marks which can also contribute to the buckling.

The materials to do hinge well are TPE, HPPE and... you guessed it, ABS. I have bent the ABS hinge back and forth about a couple dozen times, bending it all the way back on itself. It is starting to split in the middle a bit but still works. I don't know how many times you expect to bend your iPhone case open but I think it would last me for a good while. The thinnest part of the hinge is .68MM.

BTW, I had my wife stitch me up a wallet of Tandy Imitation Alligator cowhide. It holds dollars as well as credit cards, DL etc. and my "pen glasses" (reading glasses the size of an ink pen). It also holds my Android phone. I've used it for three years and love it. It protects the phone from drop-and-breaks, some weather and looks as good as the day it was made.

I put self-adhesive Velco dots on the phone as well as the wallet. I can rip the phone out if I want or, usually, I just bend the wallet backwards and talk with the phone still attached to the wallet. All the checkout counter clerks ask me about it, so hey, you KNOW its cool. 

Here's a couple pics without the phone in it (I'm taking the pic with the phone).

After printing the second layer type, it peeled off quite easily for me...

I am sure it is possible, but maybe not with this material... might need to try Nylon instead.

I was trying to design my own version of my Wife's iphone case. They also had 2 different materials used, one quite flexible.

ABS doesnt like to deflect much without creating plastic deformation and discoloring. I would be worried about bending it as much as you see in the picture. The Flexible PLA would have been perfect if I could get it to bond to normal PLA... Maybe I need to play with the temperatures more

Just a thought...if you were to build in a matrix of 1mm diameter holes in the PLA parts; and then print over that with the flex at about 2-300% first layer, would the flex flow through the surface holes and help the bonding by mechanical means.

ABS doesnt like to deflect much without creating plastic deformation and discoloring. I would be worried about bending it as much as you see in the picture. The Flexible PLA would have been perfect if I could get it to bond to normal PLA... Maybe I need to play with the temperatures more

To try it, print a rectangle about 2MM thick with a center hinge segment running across the width of the rectangle. Make the hinge about 2MM wide and .75MM thick. Maybe taper the edges of the transition down at an angle and out about .5MM for good form and to transmit some of the stress back into the body of the rectangle. Kinda like:

\__/
____

I was able get some successful prints, but it required babysitting. Both finished prints are quite flexible.

I did an experiment with the flex pla where I did a few layers of flex and switched to standard pla to see if they would bond, but it didn't bond very well. I wanted a rigid structure with a flexible joint..

I seem to have improved it by mounting a small section of PTFE tubing between the drive and the top of the hot end. This helps  give some lateral support to the filament. I had to rig up a mount for the tubing to keep it straight and rigid.

For smaller prints, this is working fine now, but on larger prints it will eventually buckle enough to jam in the tube...

its just really soft stuff.

I also bought a spool of Ninjaflex, so we will see if that works any better.