I would check to make sure what type of porthole is in the cabin you're getting. We had to move out of our assigned cabin on the Holiday on one cruise, due to a water leak, for a twelve hour period. It was the most forward cabin on the lowest passenger deck. The porthole was for a little light only. The hull is deep here and the porthole is in the outer skin. I have no idea how many cabins have that type of porthole. We could see waves splashing by at times but it was high and deep enough that you could not see out. A friend who cruises several times a year economically also had a cabin with this type of porthole one time. She checks now.
I don't think she would have minded the ledge but deep is another thing.
The cabin was fine though.
NCL-Pride of America-May 2011-Hawaii
Carnival Elation-Feb 2011-Mexico
Carnival Elation-Nov 2010-Mexico
Carnival Dream-Oct 2010-Eastern Caribbean
RCL Oasis-May 2010-Western Caribbean
Carnival Fantasy-April 2010-Mexico
HAL Ryndam-Sept 2009-Alaska
Carnival Holiday-May 2009-Cozumel
Carnival Celebration-April 2008-Key West, Nassau
Carnival Liberty-May 2007-Panama Canal
Carnival Miracle-Apr 2006 (1st for DH)- Mexico, Belize
Carnival Holiday-Feb 2005-Mexico
Carnival Fascination-Dec 2000-Nassau