The only good honest opinion that seems to be shared here on these forums is that all the ropes are pretty good, just up to details of personal taste. Except Arbor-Plex.
But no one has really said why?

Arbor-plex is the only real arborist line I have had the chance to play on so far. It seems durable, and I think it is a bit stretchy. It perhaps seems to go out of round a bit under tension, and in the blake's hitch.

I have been studying long and hard to decide what rope I want to get. Unfortunately I can't get my hands on them to see what I think I like, so after much internal debate I have decided to go with 150' of Arbormaster BRW with one end eye spliced. Which will go along with my new tengu, a blue streak split tail, an extra split tail for the old double split tail routine. Dang this hobby is a bit pricey to start

Culinarytracker

I bough 150 ft of Arborplex because it was low cost ($70 bucks). It is a bit bulky for the average climber that likes to carry stuff around (6.2 lbs/100 feet). It tends to "pick" some of the fibers when using aggressive teeth gear like mechanical ascenders from PETZL. It tends to "grab" the rope when descending with a split tail, It does not fit inside the Grigri ( to fat for it).

Other than that I think is fine for any climber. I have used it for lowering branches becasue it is very strong. (6000 lbs)
I think we turn a little "snobbish" with our gear and like to show off that we have the newest and latest on the market. You know showing up to the neighbors. If the Arborplex rope is what you have and you like it that is all it counts.
Use it and have fun with it. Do not listen to the "gear snobs!"

Here's the point of view of a moderate gear snob. I've climbed on ArborPlex a fair amount, as well as several other types of lines (mostly New Tribe's Chameleon, and NE Ropes Safety Blue).

ArborPlex is cheap and plenty strong. If it's what you have, climb on it and you'll be safe, and have lots of fun. At the time it first came out it was a huge improvement over the 3-strand twisted lines a lot of folks used at the time, and it holds up under rough use just fine.

If you have a bit more money to spend, I think you'd be happier with something else.
My complaints:
- It does indeed square off under load, and this does not improve with time. This makes behavior of friction knots a bit less predictable, and it makes using hardware (mechanical ascenders, rappel devices) rather squirrelly as well. Furthermore, a squared-off rope is not as nice to grab on to during the climb. That said, if you wear gloves most of the time this won't matter to you quite as much.
- The loose weave that OT mentions does lead to picked fibers with mechanical ascenders, but again that may not matter if you mostly climb with knots.

There are a bunch of ropes that are more comfortable to climb with, and more versatile. But, as OT points out, it works fine and it's plenty safe.