We take the quality issues very seriously and would be delighted to address any issues brought to our attention.
We have had quality issues with labels in the past (not more recently then 4 years ago). All official Cubes should have a batch number printed on the inside of one of the corner faces which details the date of manufacture. It is possible there might still be very small pockets of old stock on sale.
The best labels are self coloured PVC (which is now a banned toy substance in many countries) and we had to change the labels as a result of that restriction. We now have very hard wearing and bright labels that undergo a stringent 500,000 times rub test under a specially designed rig. If you are going to use your Cube in competitions or you regularly play with it over the course of years you may need to replace the stickers with the PVC type available on our website - www.rubiks.com
The Cubes are made from injection moulded plastic and we use top quality ABS (not reground old plastic) and we monitor the tool wear carefully replacing or refurbishing the tools if they start to produce parts that are out of acceptable tolerance. It is true that some Cubes are stiffer than others but we try to have an acceptable limit and test all production batches to meet our requirements. If the Cubes are too loose then they might "pop" apart but if they are too tight then they are less pleasant to play with. This is a fine balance to get right and even with modern manufacturing and quality control there is bound to be some variance. Generally speaking Cubes will "wear" in and become more pleasurable to rotate the more they are used. If you are going to use your Cube in competitions or you want to optimize the rotational stiffness then you can purchase a DIY Cube from our on-line shop which allows you to personally set the tension using a screw driver! url.
If you have any concerns about quality or you would like to bring any other issues to our attention then please do so and we will try to remedy the situation