The drug dealing really is implemented well.  I just wish the cops weren't so "sensitive/easy to rile" in this game.  I complete three missions and decided to take a break and earn some cash in drug deals.  Had a ton of stuff saved up and made nearly 40k working through some tips/leads with dealers I've talked with.  On my way to another tip, I nudged a cop car on the road and ended up with a One Star alert.  I won't get into the details but before long I had Three Stars going and all this in a part of town where I've yet to have many safehouses.  Turned a corner, lost control and hit a wall and upon trying to go into a reverse a cop pulled me out and busted me.  All my weapons (had a ton, including a chainsaw I found randomly lying in a construction site) and the rest of my drug stash was gone.  Weighing the pros and cons of still having most of my money and completing three missions versus having lost a great deal of my stash and all my weapons, I just cut off the power and will attempt it all again later.

wow im surprised this game is so awsome and fun apperently its about an asian dude that needs to protect his family honour pretty good story and fun gameplay oh yeah

Finally beat the game last night, that last mission was kind of hard for me, probably because everyone was carrying a carabiner or something.  Just slamming through drug deals now, trying to complete the in game challenges and the odd job missions you find from people on the street.  I did some mission where you had to give some lady the thrill of her life before having to retire to the hospital or something for some illness.  That was... interesting to say the least.  Not sure if it was the mission, the area of town or just the time of day but there wasn't a whole lot of traffic and I was just flying down the road, beat my record for catching airtime on a ramp and a few other tricks along with it.