I tried to find a good survey on the "pleasantness" or enjoyment in meditation. A quick online search did not find anything. I have anecdotal evidence from facilitating mindulness meditation groups. I would say I have a few thousand anecdotes from a few hundreds people.
The enjoyment of meditation varies dramatically. From highest levels of human bliss to extreme discomfort.
It is generally less enjoyable at the beginning, then more enjoyable, then variable.
Overall, people report meditation as positive, in spite of variation.
Mindfulness is not just about meditation times. MBSR gives techniques that are used outside of specific meditations. A full practice is a way of living that can happen throughout the day. I am trying to be mindful (non-judgmentally aware) while writing this sentence.
I also suggest that we pay attention to how fun it is to do a lot of activities, like watching TV, or reading internet posts. I think you'll find that these leisure activities are not even as positive as a meditation session! Stimulating, but not necessarily positive.
Very interesting topic. (Then again, I'm biased! Preaching to the choir/confirmation bias in full effect for me.) Thanks for posting.