Ok, I'll jump into this thread.

The most important concept is Rule #1- FEED THE BABY. If the baby can't, won't, or should't be fed at breast, then plan "B" is in order. Trouble is, there is no definitive research to guide us on (1) which device is least likely to compromise any particular baby; (2) which infant factors combine to suggest a particular device; (3) standard techniques and protocols for using non-breast feeding devices, (4) etc. etc. 

The attitude I'd like to make sure we all agree on is this: "plan B" is a temporary solution to getting sufficient calories into the baby that the baby continues to grow while we figure out why she/he can't breastfeed directly (which is Plan A). The aim is to establish or restore direct breastfeeding as quickly as possible. There is no "one" best manufactured feeding device, just like there are no "best" ABM recipes. All are compromises. None are "best," but some are less compromsing or damaging than others. (Maybe.) 

And then there's the mom to consider. Some have skill deficits independent of the baby's skill. However, it's rare that I see a really inept mom who can't work with her breasts as well or better than feeding devices.

And one more thing - any time a baby is having trouble at breast, I firmly believe we need to use a pair of devices - one to get the milk, and another to feed it to the baby. If the baby can't, won't, or shouldn't feed directly at breast, then Mom needs to maintain her supply by frequent removal of milk somehow. Breasts come in pairs; if the baby isn't at breast, then a pair of devices is needed until the baby can get back where he/she belongs - directly at breast. 

Linda Smith, Dayton OH
Bright Future Lactation Resource Centre
http://www.bflrc.com/bflrc.htm