Hi, I've been a GKR Gold member since 1994, done a few years as a branch instructor and also recruited new students for them. There is plenty of excellent training you can get from GKR but it doesn't cover all areas of Karate as it is a family club with sporting values as opposed to a traditionalists style of club.
There are a few things you should be aware of though to avoid any disappointments;
GKR the school
The style focuses on non contact sports karate. This will develop your fitness and confidence. It doesn't however allow for break fall training, and grappling seen in other schools. This will put you at a disadvantage when it comes to self defense. In addition, contact and body conditioning isn't encouraged by all instructors and so you might miss out on this compared to say Kyokushin who have a contact form of sporting competition.
The quality of branch instructor technique is extremely variable. Often the main characteristics chosen when picking branch instructors is their attitude and ability to communicate to students and keep them motivated with positive encouragement. If you are looking to be inspired by an excellent practitioner though you will need to travel around a bit. There should be a senior class in every region that you should be attending from orange/green/blue belt onwards, depending on the regions limits on senior class intake. Not traveling to new classes, including classes outside your region, will only slow your progress.
GKR the business
GKR doesn't really follow a normal financing structure for those building the business. There are active scripts to be remembered which contain many word tricks and persuasive language. Regional Managers run a business of selling their job to others so they may become like them to build their business.
This business model suits many who have adopted it and stayed with GKR for many years but has also disgruntled many many more who have felt lied to, tricked and cheated by GKR managers. There is a heavy emphasis on attitude training (brain washing really) via educational and motivational material and some standard business laws such as demographics of a market are met with plain ignorance (example;"there is no such thing as a bad area, just a bad you"). It shares many similarities with the practices seen in organized religion, multi level marketing schemes and old school 80s pyramid sales.
I can say that the organization has changed a lot since I started. It has become more sports focused and has cleaned up it's student recruitment programs with higher levels of quality control to monitor what message is being sold to new students before they attend their first class by consultants. The curriculum has been refined and the style is consistent across the continents.
GKR isn't perfect but no club is really. I see a lot of the issues that GKR faces in many of the other clubs.
All in all it is a perfectly suitable club for anyone who wants to learn the fundamentals of karate and fitness in a positive, sporting family environment.