I successfully upgraded from 2.4 to 5.1 at http://www.jacmus-prime.net last weekend.
I've just come across a couple of small problems with the Image Galleries feature.
I can't upload anymore When using Firefox it says the upload is successful but then never uploads the image, and in explorer I just get a white page.
I've also had an issue with image plugin where the image would not show and after I kept trying to redo it it then put the word "image" on my page.... I decided to leave that one go for 24 hours and now it works again. No idea why it wouldn't work last night - I tried everything to get it working!
All my images are stored in the database (which I ran the conversion program on during the install dialogue).
I really like the image galleries feature and will be very saddened when its no longer a feature of wiki tiki I understand that I could use the file galleries but it doesn't have the same features or look for the images it uploads.