I have one. Unfortunately, its an older model that has plated shiny drivers that get crapped up easily. That was fixed on more recent models. Other than that, I find it to be a little light and geared too fast. I rarely run mine and its slated for a future bash.
The Aristo 0-4-0 can be very reliable as long as you don't overload it.
With a new motor it can pull trees (slight exaggeration), but if you run it heavily loaded for hour after hour, it will overheat the little motor and the motor won't have much torque and tend to stall out until one day it burns out a winding. With 2 or 3 cars, it will run happily for hours. If you do cook a motor, you can change one in about 20 minutes for less than $15. A fresh motor pulled 2 sierra coaches and my tender aournd the asylum layout with 5ft curves for months, but overheated in about 8 hours with 3. I used to run the asylum layout all day almost every day.
If you have an old one and the wheels are collecting junk, Aristo will overhaul it for like $20 and make sure it has fresh motor, the latest wheels, working smoke generator, new detail parts and so on. Some have complained of the newer wheels getting pitted, but the "pitting" can be easily rubbed off with a track cleaning eraser.
As Dan points out, extra pickups in a tender help it drastically. This is just the nature of any little 4 wheel loco.
Here's one of mine dolled up with some green and black paint, class lights from Ozark Mineatures and a scratch built tender. The tender has power pickups. I tore up a gear trying to pull 3 coaches (those are heavy) up a 5% helix later that day. Oops... $20 to Aristo.
Oh, forgot to mention. Stan Cedarleaf made the 98 decal for me.
I have one that is about a year old and had some up dates. It's a good running loco but you still can make it run better by adding the tender and then add the additional pick ups from the tenderto the loco. Later RJD