We're up to 11 now!!  I've helped three that zipped and then stopped for 12+ hours... so far all three have been just fine, no blood when I was helping.  They seemed grateful, honestly.  
  I have one more that pipped a big hole but then stalled... we're giving him until after work this afternoon and if hes still with us then he'll get help too.
Interestingly - all but ONE of my chicks are Valleys.  Only ONE blue scale hatched, and only 4 of the blue scaled pipped at all.  Maybe they need different conditions.  The seller did warn me that the weather was bad (?) the week I ordered so he only had 12 blue scale eggs and couldn't send the customary extras.  On top of that almost all of the clear/infertile eggs I found (about 6 or 7) were blue scale eggs... so maybe this batch was a little off.
I'm not sure if I mentioned it, but I did this in a homemade incubator made out of parts from my junk drawer, so my conditions may have been less than ideal...  I used a styrofoam cooler with a 40Watt brooder lamp for heat.  I took apart a picture frame and stole the glass to make a sexy double-paned window.  The eggs rested on a wire platform with a paper towel over it, and a water trough with sponges underneath.
Originally I tried to control temperature with a lamp dimmer, but it varied too much.  I added a PC case fan (with bling bling blue LEDS) and stole the digital temperature gauge out of my car since it had an alarm function that I used to control the temperature by using the "alarm" to switch the lamp on and off...
... so that probably explains the difficulty.