Well, I'm just talking spiro, my endo says it is fine. In fact I think it is easier on the body than estrogens, especially in pill form.
Without E some people experience a lot of fatigue (I havn't, except for the first couple weeks). One of the main concerns is that estrogen and testosterone seem to play a part in maintaining bone density. So in theory just talking spiro alone can increase your risk of osteoperosus. I think this is the main concern - though my endo did not think it was much of an issue.
I can get it up fine on spiro. My libido is much lower, well maybe not lower, just very different (you need a change in mindset I think). I want different things out of sex now. I don't think about it as much. I don't have morning errections, or involuntary ones for that matter. Definitly can cause erectile dysfunction in some people though.
benefits for me - less likely to become permanantly sterile, chances are I can still conceive a baby while on it, helps reduce or stop male pattern baldness, reduces body hair, reduces muscle mass, some minor breast growth.
the other issue is you can only really expect mild feminisation on its own.
hope this is helpful