^ This thread helped me immensely in purchasing my first BMW...
This community has also been absolutely AMAZING in terms of the knowledge that they possess - DIY's, gas mileage postings, maintenance schedules, tips, etc... I have been a member of this forum since 2005 but only purchased my E46 in April because I decided to take the plunge - I'm sorry I never did it sooner
Everything in this thread thus far is great advice/tips.
If you find a car that you are interested in, my advice is too look it over extremely carefully on your own, and/or take it to a trusted shop and have them take a detailed look as well. If the dealer or owner of the vehicle will not let you do that, chances are they might be hiding something.
In terms of costs of ownership - yes it does cost a bit more to operate an E46 than a Honda (first off the M54b25 takes 7L of synthetic oil as compared to 4L in my Honda). Gas: I spend on average about $50-60 more a month than I did using regular unleaded, but it is well worth it as I get better gas mileage in the BMW (8.6L/100km) than in my 4-cyl Honda - I get about 660km on a full tank (mixed highway/city with moderate "spirited" driving)
The TSX and Genesis both take premium gas and probably require synthetic oil for changes as well so I doubt there would be any sort of savings over an E46 in operating either of these vehicles as a daily driver. The new Genesis coupe comes in a turbo model, and if you were to purchase this model, that adds a whole new element to the maintenance schedule.