Most full canal transit cruises are really repositioning cruises in disguise and they usually take place in Fall and Spring. Either time is great.
If you only have 10 days, the round trip from Florida is good. But if you have the time I urge you to do the full transit. I live on the West coast so I like to fly first and then just sail home. But either direction is great.
As for the "watching paint dry" comment, whoever said that must be very very hard to please. How you can compare a first hand look at one of the marvels of human engineering to watching paint dry is beyond me.