My overall experience was incredibly bad.
I was a contractor and applied for an employee position. The whole process took around 3 months. I spent most of this time just trying to get answers... The HR person told me that I would be contacted for an on-site interview in one week. No news for 2 weeks, so I wrote an e-mail. They didn't apologize, just told me it would take another week. Ok. Finally, I went to the on-site interviews.
The interviewers were not professional at all, they obviously lacked experience and/or interview training. On top of that, half of the questions and exercises were irrelevant to the role I was applying to. Most of the time, I was wondering why they were wasting their time on irrelevant questions and when will the real questions come. The real questions never came.
At the end of the on-site interviews, I was very disappointed. I thought that they hadn't done their job correctly, I half wanted to go back and tell them how to do it properly next time. As a result, they didn't really know what competences I had or lacked for the role.
I hadn't failed the interviews per se, but I wasn't confident on the results either. So I waited for the answer. Needless to say that they made me wait again. They told me I would have an answer in a week but didn't contact me (yes, again). I sent them a friendly reminder 2 weeks later, they ignored it. I sent another one one week later. They finally answered. An HR person told me that they didn't select me. So I accepted an offer in another comapny. Then, 2 weeks later, they contacted me to say that they might have made a mistake and wanted to offer me a position later the same year. I mean, seriously...
The lack of respect, the lack of professionalism, the lack of organization, everything was so low-quality.
Of all the interviews I have done (Amazon, IBM, Google, and smaller companies), this was, by far, the worst experience.