The Weaver S3 Northern is an excellent runner, with this caveat: ALL brass engines are hand built, limited production items that can be futzy, have strange problems, and be difficult and delicate to handle. Within that universe, IMHO the Weaver S3 is one of the best. I've had mine (#267) for about ten years, run it a lot with heavy loads, and it looks and runs great. However, I have had occasional problems with it. Once the motor mount screws loosened up and it wouldn't run right because the motor was jumping out of place. Fixing it was no big deal once I figured out what was wrong. Recently I had a crosspin fall out of a universal joint and it stopped working until I could make and install a new pin. Again, not that big a deal to fix and no cost since I did it myself, but it was time consuming. I've had occasional issues with the smoke unit (pretty typical of ALL Lionel and Train America smoke units built around that time). Now, I consider the problems I've had with the Weaver S3 to be minor, although they've been time consuming to fix because working on a brass engine is a delicate and time consuming operation. Weaver has superlative customer service and Gary, their service guy, can fix anything (mostly I just talk to him on the phone and he tells me what to do). If you can get a good deal on one, buy it - but understand that it's not your grandfather's Lionel train.
As far as a VO-1000 goes, I'll stick with my previous advice - be patient, wait until you can find a Weaver with a factory Milwaukee paint job. I really like the first version with the early orange and grey paint job and four stacks. Weaver does a really nice job decorating their engines. Unfortunately I don't have a photo to post. I'm sure the MTH ones run great - everything I have with PS/2 or PS/3 runs great - but you're in for a bunch of money for a paint job.
