A couple of thoughts from the class of 1989-1990.
Ameriflight training hasn't changed. The Frasca sim mated to the chieftain cockpit was new when I got there. I was an IP and I begged and pleaded to do offline training. I bet the heck out of doing single engine work fully loaded and at max gross weight. The training was designed with one thing in mind: survival. There was no captain to help you out when things started going South. Embrace the training and the experience. I had people tell me that Ameriflight was the best stick and rudder flying they did in their careers. I can now agree with that assesment.
Is having Ameriflight on your resume a good thing. All I can say is that if the recruiters know anything about AMF, it will be a positive. If not, then it's just another job on your way up the ladder. Something that you can't put a value on is that for the period starting mid 1980's to mid to late 1990's, there were a lot of pilots that worked at Ameriflight. These pilots, like me, have risen up the ranks and now might be in positions of influence at 121 carriers. I would look highly at a former Ameriflight pilot and would view his experience in a positive light. Do you need this to get hired at your next regional, no. If I saw a resume with Ameriflight experience on it, it will get a harder look.