We used them twice on homes we were C/S on to help make us confident in buying our first home.
First inspection went really well. They found a main line leak and some other issues. Was really impressed. However other concerns, unrelated to inspection, caused the deal to fall through.
Second inspection was on the home we purchased and now live in. This home is a bit of an odd case as it was renovated 3 years before, but was built in '76. The inspector (diff from first time) did a "tolerable" job. They identified a few things, including one that we tried to get warranty for from Amerispec. The owner had the laundry taps turned off as she said she was "not home much" when we asked. The inspector turned them on (which is great) and ran the washer/dryer. All good. BUT he didn't double check that the tap connections weren't leaking. Therefore 2 weeks later, once water has seeped through cabinets underneath the taps and through some crappy linoleum I have a minor flood... needless to say I was not impressed. A) by my seller who definitely knew and didn't disclose to us, even after asking. B) that the inspector was not diligent. Amerispec would not hold up on 60 day warranty we had (and were way within timeline) as the water had been off to start with. A bit annoying as there is no way I can force the seller to turn water taps on... in the end they didn't cover it and we ate cost (as our seller, whom we had other major problems with, just disappeared without a trace).
I'd say that it's 50/50 on this one. 50% my realtors fault for not getting reason for water off being in writing (that realty company disputed as it was verbal) and 50% Amerispec for not checking and then not holding up warranty.
That said, the gentleman who did the first inspection and seemed to do admin work was very helpful and great. I wish he had done our second one. So I don't hold Amerispec entirely responsible. However, do feel that it could have been covered under warranty (which they have insurance against so it's not like it's direct money from their pockets to fix).
I'd consider them again... but also look at other companies ahead of time before deciding.