To the OP: I would keep doing research. We did a lot of research before sailing on the Pacific Princess in April, and 99% of what we read was very positive. We, on the other hand, had the most horrible experience(s) we've ever had on a cruise and will never be back.
We have sailed on most every X ship but the Infinity. Like you, we were interested in the Panama Canal cruise. We just booked it! We're sailing in September. I hope it's as good as our other X experiences. What I like about X (regardless of ship) is for us, they seem to always take matters to heart and attempt to change what is displeasing us.
Our friends who sail HAL and X took a 2-week on the Infinity to Hawaii in 07 I think. Although this was almost 2-years ago, they told me today they loved the Infinity and didn't have any complaints.