Heres the basics:

- no, it isnt particularly important to her. I dont think our relationship would really change much either way.
- that said, it isnt really that important to me either to have the title of being married.

That said, there are two big reasons why I want think it would be beneficial:
1) My ex is re-married already and while the new spouse isnt incredibly involved with my kids, there are some various events that I feel awkward inviting my partner to that I cant really stop him from attending because of the title. For example, my kids parent teacher conferences - I cant block their stepdad but I feel weird inviting my partner because of that title thing. So I think to give some...legitimacy to the relationship with my kids, the title has some meaning.
2) While she is employed, she doesnt have health insurance through the employer. So, almost $5K a year is being thrown away on an extra health insurance plan that isnt really any good. My coverage wouldnt change with her added.

Neither of these are good reasons by themselves to get married. But maybe help in case of a...'tie'?

The biggest negative is the financial implications. Im still on the hook with my ex for SS and CS for some time. I cant really afford another set of payments or another division of wealth. I feel like Im just starting to get back on my feet after around 2 years of financial backsliding.