bitcoincharts.com:
Can you estimate the chances of success for each company? I don't.
Got it from vircurex, but the actual hashrate isn't the point, nor is the growing hashrate of LTC. The point to my mind is that BTC difficulty is low and may be dropping further with the delay of ASICs from two of the three companies.
As for estimating the chances of success from the three companies, while I agree it's subjective, I reserve that call for myself.
Avalon:
At this point I believe Avalon will be first out of the gate though their first order was small(300ish?). The odds that Avalon is a scam is near 0% to my mind. I do not care for their choice of 110nm or the stand alone aspect of their product, but I do understand their choice in both instances.
BTCFPGA/Bitcoinasic.net:
Next up is BTCFPGA in my mind. Yeah they had a big setback and Tom was AOL with some undisclosed family matters, but I believe their issues can and will be addressed. This company has/had a good reputation for meeting timelines/specs. Also they're the cheapest per Gh, and now by a significant margin. Very low chance they're a scam to my mind < 10%.
BFL:
I believe they will be last despite announcing first. They do not yet have chips and the chips are coming from Asia. They've announced flaws with their past chip revisions and then retracted and said they just wanted to make them more perfect. Repeated delays and a general lack of straight answers as well as a history of delays and missed specs makes me doubt this company can pull everything together before either of the others. Highest chance they're a scam, but still < 25% IMO.
Lastly, though I did find the exchanges between Tom and Inaba/Josh rather disturbing and unprofessional I do not see evidence that Tom reacts this way to customers or potential customers, rather he's very friendly and personable when not involved in an exchange with Josh. I've spoken to Tom on the phone and I trust my instincts, he'll come through. Inaba/Josh on the other hand treats nearly anyone and everyone with disdain and contempt. I cannot do business with this company as long as they employ such a man as their COO.