Edit 5:04 EST 11/21/12 This locmotive died after about 20-25 minutes run time total. I post some info about that at the end.
-----------------------
I bought the MTH 999. It is a nice little loco. It takes a long time to decide it is going to have to run in conventional but after that we got along great. Smooth runner, runs at a pretty slow speed in conventional (despite the "land speed record" 84" drivers and pulls six cars -- all I tested today, nicely. Nice lights, very good sound. This PS3 loco does have sound obviously better than my PS2 locos (another PS3 loco recently acquired left me undecided) - sound nearly as good as the best Vision or Legacy locos, and with such a small tender, too!. Weird whistle. Detail is good, paint quality good, etc. No too much detail, but then I don't think there were too many details to model.
Altogether, I rate it as equivalent in conventional running capability with and much like the WBB Baldwin ten-wheeler (a bit smaller though) in "feel" and stature on the track, but with slightly better quality of detail AND very good sound. I like really the sound- very rich chuffs. Definately worth the $500 I paid.
Remember this is a scale loco. Here are pictures of it with the scale Lincoln funeral train loco and an old and very tired General.