I've also been interested in injections - seems like it would be a lot more convenient, and I do just a touch of partying, so it'd be better for my liver. Both docs that I have been to have been apprehensive about injections - the first one tried to talk me into the gel, and the second one was clueless about everything. I guess the thought of having people injecting themselves makes some docs uncomfortable.
One big tip about getting your spiro cheaper - do it through Costco online. I was getting my script filled at Walmart and paying about $65/mo, and now I'm paying about $20/mo. Mail or fax in your script, and they'll fill it for you. Also, ask your pharmacist to get the spiro filled in lower doses - i.e. instead of one high dose pill, fill it as multiple lower dose pills. This cut the cost down to like to like 1/5 of what it would have been.
Oh, and Costco's estradiol is also dirt cheap - I'm paying ~$5.75/mo, but estradiol is dirt cheap at any big pharmacy.