I had my eye set on the Flip Mino HD, but after hearing the touch sensitive buttons can cause problems while recording, I decided to go for the lesser Flip Ultra and save the £40.
There isn't much to cover other than the Flip ultra does what it says it will, a reasonably priced, small, good quality video camcorder with direct upload capability.
My only niggles with this camcorder is that it is slightly bigger than I had anticipated (larger than the average mobile phone) and that the screen seems very small when compared with other rival camcorders and mobile phones.
If size is on the top of your priorities then I'd say the more expensive Flip Mino HD is suited better for you.
I can't complain with the quality of the Flip Ultra and the value for money, but I'm still not decided on whether I wished I had went for the Flip Mino HD instead.