I have a C0636A (bought new in 2017), it is my go-to machine and as an amateur hobbyist, it will be many years before my skill exceeds its capability. As a comparable, it is part for part identical to the PM1440E-LB -- as in identical.
I purchased mine from Modern, and the batch I bought from had the 2hp motor swapped for a 3hp (they said they did the entire shipment after a couple of failures in the same batch -- just saving them the service call).
My only complaints with the machine are 'advertised' speeds and gear-box configuration.
The speed selector indicates top speed of 2000rpm. As delivered, the machine did 1675rpm, which I narrowed down to a single gear in the headstock. Modern figures the factory used a different gear to accommodate the larger bore. Not sure if this was a limited issue for the batch. If speed is important to you, I'd have Modern run it up and test it. The fix for me was to change the pulley diameter from the motor. I now have the top-end speeds matching, but the low range are slightly faster. It was one of the other.
On the gear box, you WILL be changing gears if you want to cut any variety of threads. Yes you can cut different pitches with a single gear selection, but to cut standard common/fine threads in the 3/8, 1/2, 7/16, 5/8 and 3/4 range will have you changing gears more often than you think.
The pros for the C0636a: Well equipped (DRO/taper-attachment/3 & 4 jaw, steady/follow-rests etc., Free delivery (Calgary), serviceability from Modern (vs. King/Busy Bee etc.), and a physical throat to choke if there were issues vs. email/phone. (there were none). I decided to buy new as a way to hedge wear/abuse issues on buying used -- this is a foundation machine for me. I bought used on my mills, because I haven't decided which size/style I'm after yet, but the lathe was something I was pretty dialed in on.
Now, there are different variations of C0636 lathes out there, the 2" spindle / D1-5 didn't show up until the newer batches. The older C0636 had the ~1.5" / D1-4 configuration.
@Janger and I recently compared threading setup and his C0636 (older model) had way more options for threading (has setup for module).
My assessment here is based on never running a heavy/high-precision monster such as a Colchester, Monarch etc. but I have run smaller, lighter lathes and can appreciate the difference between those and the C0636a.
As for accuracy, I consistently find that my issues are operator/tooling/technique based at this point, and probably will be for many many years.