I have ~13,000 miles on mine and have had nothing whatsoever go wrong with it. I use Mobil-1 synthetic (10w40) and change the oil twice a year. The drive shaft splines and joints need to be greased each time the rear tire is replaced, but that's really easy to do. The swingarm is supposed to be serviced at the same interval, but if you install a zerk fitting on it as per these instructions
then all you'll have to do from then on out is hit it with a grease gun during each oil change. Both bikes are shaft-driven and water-cooled, so maintenance should be similar.
The more reviews you read, the more evident it will become that the VTX1800 flat out has more power. However, what led me to purchase the Mean Streak was its superior handling and braking. It's easier to improve engine performance than overcome chassis and braking deficiencies, and handling was a big thing for me coming off a sport bike. I had a chance to buy an '03 VTX1800 brand new for just $8,000.00 but passed it up due to the first review I posted and having sat on one to experience the weight for myself. That is not to say the VTX1800 is a bad bike, because to say so would be ludicrous. I'd be proud to have one in the garage right now but, for me, I think I made the right choice with this bike.