I think I am a good solver also with killers (I started my "career" with killer sudoku ) but I found this puzzle extremely difficult. I succeed in solving it just yesterday night, half an hour before midnight (anxiety ).

At a certain point, no strategy at all and a lot of possible paths in front of me, so many to discourage trial and error attempts...

Did anybody feel my own impression?

Usually, I trust a lot in the difficulty rate, but this time it wasn't so high (147.1), nevertheless the solving has been very tough...

It was definitely quite tricky. I managed to fill in or have pencil marks in columns G to I, but it was difficult to get a hook into the other 6 columns. I decided to run with one of two options for a particular cage and luckily, this proved to be the correct option and I managed to complete it on Friday.

But I note that it has only been solved 138 times, compared to an average of over 280 times for the preceding four weeks. So it definitely caused a lot of people a lot of problems.

Exactly Paul. Columns G to I were filled at first. Then... almost no clues!

For reference, here's the puzzle:

It was reasonably tricky, but if you take your time it can be solved using analysis.
After getting a lot done in the right 3 columns, it then seems that any adding of cages does not give much away, but there are several groups of cages that can be added and there is a lot of overlapping of those groups, and if you look at the way they combine the solution can be found. The d1-f3 3x3 box, especially cages f1 and e3 seemed to be at the centre of the action, horizontally with rows 1&2, vertically with column f, diagonally with cells e4 & a7, and also the cages within the 3x3 box can be added, and this is the key to finding the solution. Individually each group of added cages tells you very little, but look at how they work together and the possibilities become very limited.