Just to come in here from a purely front-end perspective, text-indent and position absolute solutions suffer from one major problem: You’re browser its still painting that text, just really far off to the left. The font:0/0 a;color:transparent; method is equally robust and has the added benefit of not painting the text on the page.
Better page performance.
As for the SEO… You’re thinking about it too much. Google is full of some really smart people and as long as the intent of your markup is clear you can be sure it’s going to come across just fine.
More and more I’m coming to the opinion that SEO is a byproduct to high-quality content that’s semantically coded with good accessibility. If you do that Google will figure it out.