I fight with mine (Thompson) all day. Just kidding. When it's good, it's very good.
You are limited to regular envelopes. By "regular," I mean NOT catalog or coin envelopes, as the shingling would mess things up with the flaps.
I have ran plenty of announcement envelopes as well, yet found no success with the likes of remittance envelopes.
Other than that, when staying within the confines of how it can be logically used, AND if it's kept properly maintained, you can run wide open every day, all day long, and grin all the way to the bank!
I bought a used ABDick 1200 (perhaps, the same as Press Specialties) several years ago. Got ripped off by the seller, as it needed a new clutch assembly (which costs more than what I paid for the thing!). I had never used one, but everybody I know that has one swears that they are the best for small presses.
(By the way, I have a used ABDick 1200 for sale, if interested. Of course it works ..... at least that's what the person who sold it to me told me!) : D