To give you my boating credentials, I spent my honeymoon on the Shropshire Union and Llangollen canals and it still rates as the most amazing holiday I've ever had. (We actually had the holiday booked before we decided to get married and make it the honeymoon!) I've also navigated the Grand Union (Linslade up to Stoke Bruerne), North Oxford and Coventry canals.
I love being on a narrowboat, it's so peaceful and relaxing. I particularly like the fact that you really can't get lost on a canal, since there is only forwards or backwards! For someone with my lack of a sense of direction, this is especially important! *happy sigh*