^ ^ Why dost thou tread in my domain?

JFWY
My Z is my daily driver and it's been nothing but a champ. I put between 425-450 miles a week on it just through commuting, it's got a little over 106K on it now.
Outside of the normal oil, tires, brake pads stuff all I've really had to do to it was have a windshield replaced and the had to repair the latch on the read hatch. The catalytic converters kept popping an engine code so I had Nissan replace them (there's a federally mandated 8 year/80,000 mile warranty on cats). I'm due for a new clutch and will be upgrading (by choice) my brake rotors. But that's it. Avoid '03 & '04 models (power window problems), the RevUp version of the VQ35DE ('05 35th Anniversary, '05 track model and all '06 models - manual transmission only) has been known to have oil consumption issues, '06 & later models have better headlights. If you can, try to find an '07 or later model.
Parts will cost more than they did with your Tib, but there's always deals to be had and the internet makes getting the best deal pretty easy. Do some online research on some common replaceables if you want a good idea of what you're looking at. Tires and premium gas will be the two big ones I'm thinking. I get anywhere between 24-28 mpg depending on how much I'm on the gas. I drive rain or shine and even in the snow. With the right tires (I'm running Bridgestone Pole Position RE960AS's but looking to upgrade next winter to Continental Xtreme DWS) I've found the Z to be nothing but sure-footed with predicatable behaviour, even in the worst conditions.
Cheese is right about having more room in the G35, but the Z is fine if you're not looking to haul many people or much stuff around. I looked at the S2000 and the Boxster for sporty DDs before I settled on the Z. The S2K was certainly too small, and I felt that I was having to pay too much for the Zuffenhausen nameplate on the Boxster.