Armen, I owned a new Silver 2003 model. Drove it for 5 months and sold it. I don't have an E90 yet to compare to so I'll compare to an E46.
Pros:
350z is called a Japanese muscle car for a reason - it's got great off the line/down-low torque! That combined with its super sensitive drive-by-wire gas pedal makes for awesome acceleration from a stop. Clutch is light and easy to use. Generally, the VQ35 engine it has is very torquey and accelerating/passing is a joy.
The car is a great cruiser and is not twitchy and is stable at high speeds. In stock form, I'd say it handles better than a stock E46. Nissan took care to make this thing setup to handle great from the factory (just look at the huge cross-brace in the trunk). Its suspension is sprung real tight and there's minimal body roll. The car is just super tight. Actually a lot of older owners who bought the car without really test driving complained how the car gave them back pains cuz the suspension was so hard, but I like my suspension like that (so this can be a pro or a con depending on the person).
Looks are subjective, but I thought (and still think) the car looks great from the outside. Aftermarket mod options are plenty. Decent (not great) value for its price.
Cons:
While it has great tourque down low in the RPM range it quickly runs out of breath up high. The e46 has more reserve power in the highest RPM range and the engine feels much smoother if revving high. Some people might like a very sensitive drive-by-wire throttle but I hated it. The slightest dab and the car would surge forward... sometimes it'd was a real pain having to modulate the clutch very carefully to avoid this surge. The e46's gas pedal has a much more natural resistance and progressive feel to it. I hated how the 350z sounded at a high RPM, felt like the engine was working way too hard. Shifter vibrated in the Z, especially at high RPM's... made me feel like the transmission was gonna give out in any high RPM runs... you could literally see the stick vibrating at a top RPM run.
Handling was real good on the car, but it lacked the razor-sharp nimbleness I'd expect from a "sports car." Steering was assisted too much in the Z... took away from the feel of the road.
One of my biggest peeves about the car was that it looked so great on the outside, but the interior quality was crap! When I first saw photos of the interior I thought it looked like it may have some quality to it, but when you actually own the car you come to realize that quality of the materials in the cabin just aren't that great. Also, the shape and positioning of the cabin just made me felt like I was sitting in a $30k tub. The worst is on a nice day when everyone else has got their windows down and tons of light and air in their car but you've got these little slits called windows rolled down, with your elbow propped above shoulder level cuz the doors are so damn high. Oh, and the trunk, with that cross-brace is absolutely useless. I had more useful storage space in my S2000, literally.
Anyways I sold it not because I didn't like it (it was still a fun car to drive and looked damn good on the outside) but becuase my payments on it were real high and weren't justified considering the cons I listed above. Hope that helps.
Armen, I must ask, are you considering one instead of E90? 