Well, the one I just got rid of was an '07 328i 6-speed sport package. I've had 7 over the years, and most have been manual tranny 3-series. The closest I had to the G8 was a '97 540i 6-speed, but I would say the G8 GT drives a lot like a late '90s 7 series, which I never owned but drove a handful of. Overall road feel, solidity, handling, comfort in the same ballpark but the G8 is WAY more powerful (and would even take the 12 cylinder 750 of the era I'm quite certain, drove one of them once). The 3-series, particularly sport package/M cars are more connected and involving than the G8, but I needed a bigger car and am actually enjoying kicking back a bit (and kicking my ass back into the seat at will). Time will tell as far as reliability. BMWs are built like tanks, extremely rugged with a high threshold for abuse, but they do tend to have maybe a tad too much engineering, more crap to break. For about the same price as a new G8 GT, you could get an '03 M-5 with some miles on it, have a blast but pay through the nose to maintain once the 6-year BMW certification runs out.
Welcome over from the "dark side" LOL! I made a trip to north central IN yesterday (560 miles round trip), and I can't believe how many BMWs I saw on the way. I actually saw more BMW 7 series than G8s! There seemed to be a BMW 3 series or M-car at every turn. At one point I saw 3 various 3 series cars around me at once outside Chicago. You will definitely stand out alot more, with more power, for alot less money in the G8. Welcome aboard!