The link provided will help, lots of useful info onthe GTR/C14 there:
my opinions on your list however:
1. Two up: no idea, single and loving it
2. Reliability to date: I have only 26,000km, so far nothing rattled off, failed beyond the standard (recall) issues (glovebox; bag locks) although I've also had loose header nuts as have many others....I have a great service/dealer...tyres, mine have averaged around 6-10K km each set (with fronts retaining some more life...)
3. Cost of ownership (maintenance, frequency, etc.) no more, infact somewhat less cost of servicing than my previous BMW...
4. Any known issues to be on the look out for or must have farkles: the exhaust header nuts seem to be the most common issue, some folk have had warped discs; farkles, many... bar risers, peg lowers, good range of racks around, also good range of touring screens too..
5. Commuter (to/from work in the city - Detroit) capabilities: it does get warm if you're sitting forever in jams, it's a little wide to split, but performs fine in traffic, very tractable and light to ride at low speed..
6. Overall Comfort: I thought the factory gel seat would be great, till I found it rock hard, since enjoying the standard seat with the airhawk-seat cushion for longer rides...I have bar-risers and peg lowers, for me its now brilliant for all day..
7. Handling characteristics: jeckel and hyde, but with good manners...can hold boring legal speeds with ease and comfort... give it a twist and it becomes a phenomenal fun rocket, smooth launch into the 200+kmh as quick as your happy grin turns to laughter
8. Gas Mileage & type: it sucks the fuel when you twist, but most get around the 40(us) mpg+, not the most eco but...the performance outways the adequate economy...
Ride style 95% street with the balance hard packed camping/fire trails.: I didn't like it in dirt, didn't seem happy/secure and I couldnt imagine it on its side and my weakling frame tying to pick it up in between bouts of tears
Me: 6'1" 190lbs. 32" inseam; Her: 5'5" 140lbs. You'll be fine, I'm only 5'6"ish and about 125lbs....
Test ride one longer than around the block, they're quite fun