IKC,
I mostly cruise inland, but have been up on Puget Sound, San Juan area and Galveston/Houston Texas areas.
There is certainly not a problem running at good speed in 2-4 foot waves, but over that it'll depend upon many factors. Usually in the 6-8 foot waves, we just have to slow down and slog it out with everyone else, but it is very comfortable the surf the swells when the seas get up high. That lifts you out of the troughs.
A guy from Hawaii was saying, as does Dr. Bob of Thataway, that the space under the platform between the hulls is not high enough to clear large seas at speed as it is in some catamarans. My experience is that the Tomcat 255 is seaworthy in high seas in much the same sense as the normal C-Dory hulls are - they run shallow and are very maneuverable so you are not locked into a position going thru the waves as with deep V's. However, you cannot just pound thru 6 foot seas at 30 miles per hour. You'd have to slow down.
I've run for several years and never had a problem with sea water getting into or damaging the Honda outboards on my boat, but I am not on the ocean much of the time. When coming off a plane, I slow gradually as one does on most boats.
All the different Cats have different performance based upon the deep V, inter hull clearance height, etc.. Several guys here fish out into the Pacific with TomCats and they'll probably chime in better on the high seas performance than I.
I love my TomCat and would not trade it for a Glacier Bay or similar Deep V cat design.
Good Luck,
John