I can vouch for the Chinese "GY6" 4 stroke complete and all - out "cheapness" 100%.
I have been a motorcycle and scooter technician for the past 15 years; 9 yrs at a Honda dealership, and now at a shop that specializes in mainly ALL scooter repair. Chinese "clone" 50cc scooters can be purchased anywhere from $300-$1000 (and that's for a brand NEW scooter). They have problems everywhere. Electrical, engine, fuel system, suspension, crap batteries...etc.
We usually see problems from 0 to 300 miles. There have been SO many cases of where the buyer buys a new scooter online, and it never even can be started. Usually this is due to whatever solution the mfg puts in the fuel tank to preven rust during overseas shipment to prevent rust. This orange, "oily" solution eventually makes it's way to the carb, clogging it before it ever sees fuel. We also see batteries that will not hold a charge from new, electrical wiring probs where the starter will not work because faulty switch, bad starter relay, & bad brake switches. I have replaced at least 100 regulators; the Chinese have not perfected their regulators at all. A bad regulator causes the headlight to burn really bright, and blow. I have seen Chinese belts break within 200 miles. Most GY6 50cc scooters have a front disc brake, and alot of times they leak from new or "chatter" when applied. The 50cc GY6 rear centrifugal clutches "squeal" from takeoff and often blow apart. Their roller weight outside surface is nothing more than cheap plastic. Even the kickstarter assembly have constant probs. The tolerances and metal quality is poor, which makes for a weak link with the kickstarter. When a GY6 50cc is getting no spark, 80% of the time it is the CDI box has blown, or the coil stops working. Lastly, alot of 50cc GY6 scooters are INSANELY slow and underpowered. On the other hand, I have done at least 30 full top-end rebuilds on a "50cc" GY6, and when I pull the cylinder and piston, it turns out that in fact the engine is a 70cc or an 80cc. These scooters are pretty quick, but were sold as a 50cc. I have read that in many cases the Chinese companies simply use what parts they have an excess of during production.
As for the 150cc GY6's... the most common probs include: after approx 500 miles, they get impossible to start. This is most always due to the valves getting extremely tight (due to heat) so they require adjustment. Guys on GY6 150cc forums set their valves incredibly loose due to this.
Next, the 150cc GY6 seem to blow stators constantly. (especially the brand "Ishimoto") Usually happens around 1500-2000 miles.
Another common problem with the 150cc's is carb quality. Their carbs are really finicky, and some carbs are impossible to adjust from new. Sometimes even the air filter has to be removed for them to run correctly, and replaced with a less dense material. We have replaced many new scooters' carbs with replacement new Chinese carbs, and they still do not run as they should.
A common trait of ANY Chinese scooter is the body parts are made of the cheapest, most brittle plastic out there. The plastic will NOT survive a crash or a tip-over, let alone careful disassembly.
It shatters!
Anyways, remember this when it comes to scooters: You get what you pay for.

I will vouch for Tawainese quality. Brands like Adly Moto, Keeway and SYM make some top-quality scooters, AND come with warranties. As well, they run great. We sell these brands, and other than oil changes, tire changes, and basic maintenence, we never have issues out of them. SYM scooters in my opinion are the best Taiwanese scooters out there. SYM's quality is right there with Honda.
Hope this helps killerpancake-dude. If you DO end up with a Chinese "piece," you will end up paying in the end for parts and service. As well, if you choose to go Chinese, look for a 2 stroke version. They are NOT great either, but genearlly hold up alot better (and run better) than the 4 stroke GY6's.
Let me know if you need help. Or, you could just go with a Honda!!
- jon