The stability will be nice, and I think the extra work will make for a nice hobby!I'm looking forward to it too! I have a new 120 and would have loved to go bigger. That 30 high and 30 deep is amazing. I will definitely follow the build thread to see what you do with it.
There are some advantages of going bigger like more water volume means things will be more stable if you make a slight mistake. It will be more work for water changes and more scraping of glass. But the flexibility of inhabitants in a tank that large more then makes up for it in my opinion.