I got married here in June.

Pros:
My out of province guests were blown away by the location and the food.
The ceremony spot is breathtaking and the views from the cabins very lovely.
The hot tub area is awesome.
Children enjoyed riding their bicycles around the resort and feeding the horses.
The Hornby vibe is relaxed, which helps counteract the stress of wedding details.
The owners and staff fulfilled all of our agreements and wishes with no surprise costs or missed details.
The food was fresh, interesting, and delicious.
Because our weather cooperated we had the most amazing outdoor reception, beyond all my wildest dreams. We had our dancefloor on the large, beautiful wood porch. They have couches and nice chairs and benches outdoors around the property and we watched the sun go down. Beautiful views.
They let us keep the music going fairly late.

Cons:
This is a very small rustic island without restaurants open all the time in June/Sept. This means if your guests arrive on a Thurs night they may have nowhere to eat and not even a grocery store open after 5:30. Make sure they are aware and do what you need to do to make sure people are fed.
Prices are quite high in my opinion. $5 per person for dessert whether we had squares, a beautiful wedding cake or a sheet cake, they did not want to budge. When we asked about dairy free options they said 'we can do it but I don't know how it will taste.' (For that price they better guarantee taste!!) We opted to bring our own cake but paid a handsome price for this option.
The cabins are somewhat pricey and even in a 2 bedroom you must pay extra for more than 2 people in the cabin.
The initial reading material I got before I booked my wedding with them gave the impression that they could tailor a meal to your price point. The reality is they do not really go below the sample menu options which are quite pricey (although very great food). When I say pricey I mean double what my sister in law paid per plate for a caterer in Victoria, BC.
We stayed in a cabin the previous winter and advised them that the oven did not ever fully heat up, even when we waited for over an hour. They seemed surprised and said they would fix it. It was still not fixed in June over 6 months later. An oven is quite important when you are staying on an island with limited restaurants and trying to feed children...
The small island 'no worry' feeling can be scary when you are trying to plan a wedding... if you are really picky and want every detail planned out, a full contract written up, etc, this is probably not the place for you. However, if you can live with a little 'grey area' you will be happy with the results.
If you want a reception where all guests are in the same room and can watch speeches, etc I would not advise more than 70 guests TOPS! The restaurant can hold 100 but that includes outside and out of view tables. More than 100 would feel very crowded.
The corkage fees quoted prior to paying my deposit increased by 50% by the time my wedding rolled around.

A quick look at my lists would show that my cons outweigh my pros, but let me assure you, I would not have changed a thing with the weekend. To me, the location, feeling and uniqueness was far more important than my small price complaints. And to be clear, no prices were a surprise when my bill arrived - all was discussed months in advance.

We will be back to Hornby annually (but may only be able to afford to camp. ; )

And we will be eternally grateful for the chance to be married in this amazing location, and for the wonderful food and service provided by the staff at Sea Breeze.