I did it last year 4 weeks before IMCH.
My personal experience:
Swim is very cold, and a see swim. Took me over 40 minutes compared to a 1:15 IMCH swim.
When I stopped swimming I just couldn't move. I lost soo much time on 2 friends that finished that next to me, I reached my bike and 1 was already gone, the other was gone by the time I removed my wetsuit.
Swim exit is painful on the feet over very sharp stones. But then, my feet where numb enogh not to mind too much.
Bike had traffic light in it which wasn't good. There were road works and marshals were writing down how long each cyclist had to stop. As it is a kind of out and back there it stopped me twice.
Otherwise it is along a dual carriage way and back,then a b-road and back. Overall slightly short (which on the day was nice for me).
Run is hilly, and, if you are as far back as I was, lonely. They were running out of energy drink the 2nd lap around.
Some of my friends liked it, I didn't. Killed all the confidence I had.
Personally, I don't think I will race this year before Switzerland. Last year I was nervous about it, but I think I can benefit more from a long ide and run that week than from a race.