I love Kaiser Permanente. I am an employe but putting that aside it is my primary insurance and as a member I can tell you it is a great insurance/healthcare to have. I've read some of the comments and concerns and can touch on a few of them as an employee.
-Costs: Issues with costs such as copays and/or benefits are not chosen by KP. Your employer chooses the plans and copays. Also, your employer determines the amount in which they will contribute to your portion of benefits, again not decided by KP. Another factor to consider is your fellow co-worker's health conditions can play a major role in the cost of coverage for your employer which falls down to the employees. This is the same through any health insurance carrier.
-Access: This can sometimes be an issue depending on the department/reason for the visit. I know KP attempts to have the best availability they can. For example, we allow approx 20min for visits which is the typical amount of time needed. If we lower the appt time this will cause frustration with some members for not being seen long enough. If we lenghten the appt time this will replace some available appts which will push out the next available opening.
-Billing: Healthcare is very complex and can easily cause billing issues. Although we strive to handle these errors as best as possible it is not uncommon to have problems when dealing with insurance claims which I'm sure other insurance carriers can agree on.
-Wrong diagnosis/delay in diagnosis: Of course I am not a doctor but from personal experience in the past (with other insurance) I have found this to be quite common through any doctor's office. They do call it practice for a reason. Unfortunately when dealing with health this isn't ideal but it does happen. We certainly do not want malpractice and if this is indeed the issue then it should be reported right away.

As an employee I hear about both negative and postive feedback. Kaiser Permanente is a great company for insurance, healthcare and for giving back to the community. There are a lot of wonderful aspects about KP and I'm extremely proud to work here.