Howard Porter I find rather good, I was no fan at all of Carmine Di Giandomenico's european style when he started with the series but by the time he left last year he had developed and adapted considerably to the requirements of the character, and again, I eventually found rather good on the book.
But I do understand your unease. The Flash has always been a character who is difficult to find the right artist for as it demands someone capable of creating a particular style and technique by which to show superspeed and make that visually exciting to follow in a book - I would say that so far in the current modern era only Francis Manapul stands out as such a talent and a great fit for The Flash. In past era's we had a continuous flow of such talent on the series - Mike Weiringo, Greg Laroque, Paul Pelletier, even Paul Ryan had a certain flair for the character.
This is a character who, by nature of his abilities, demands artists of a certain flair. Amanda Connor for example would be a worthwhile choice, so too Carlos Pacheco or Pepe Larraz... whoever it is they must be exciting to look at for this character. The Flash is a character who needs lots of energy visually...