I don't think there is any loyalty or fascination with them. They've just found the right price point.
You have the cheap, gaudy, heavy stuff and you have the expensive, lightweight, high quality stuff. ROTA probably fits somewhere in the middle.
The most common (major) faults on a 350z are:
Gearbox synchro issues - generally effects the earlier models (03-04)
Tire feathering issues - again, effects the earlier models. 2005 should be OK
Oil consumption issues - Only effects the "Rev-up" models (Z's with a 7500rpm redline)
Power window issues
Otherwise, 350z's are pretty reliable for a sports car.
The only other thing I can suggest is to make sure that the convertible top is good condition (no leaks etc), as with any other soft-top.
Can't comment on the price as I don't reside in the motherland
JWT claim a 6.5hp increase... but I'd take that with a grain of salt. I have one installed and cannot determine any difference in performance.
Advantages: Increase aural pleasure
It's quite possibly the most popular mod among 350z owners - I can't imagine you'd be disappointed if you bought it. An 06+ airbox with drop-in K&N filter has been proven to be the best performing intake mod, but at the end of the day, intake mods on the Z are always going to give negligible horsepower gains so you may as well get something that sounds great
Got a link to them?
I had a quick Google - I'd personally avoid them like the plague. This is just an assumption... but they look cheap and heavy with poor offsets.
I'd suggest that you either replace the Rays or look at something like ROTA's. I'm sure some of the sponsors/vendors on here will be able to assist. What is your budget?
I haven't, but I can't imagine they look much different in person. I don't like the way that you can see the individual LEDs. It looks cheap.
CCFL tubes or LED set ups on the facelift Zeds look awesome though!
CCFL:
LED:
It's possible, but there aren't very many options for the prefacelifted models as the reflectors do not come apart easily.
One option is this, although I'm sure you could do it cheaper by making it yourself. I personally think they look @*!#.
http://www.thezstore.com/page/TZS/PROD/350z04d/50-3071
I know the names are different, but the colour codes should be the same:
AFAIK Liquid Aluminium only came on the 2004's and Silver Alloy was only on the later models.