I have to say it's kind of like how PG goes on about how startups should have more than one founder so that they'll be able to carry the load together... I would not be where I am today without her continued support and I'd like to think vise versa.
That said I've dated other women who got mad if I didn't unplug for a weekend entirely and would go out dancing and drinking every night at a club. Honestly I don't know how things would have been if we had got married -- I think the relationship wouldn't be able to stand the pressures of life. It took me a long time (likely longer than it should have) to find the right person to counter balance my own weaknesses and encourage me to keep striving toward my goals.
The key isn't waiting for a time when life's pressures disappear but finding something who has the tenacity to tackle them with you.
Be good to each other and I think you'll be fine.
Being single is not an advantage at all if you have a healthy marriage. I don;t really know what happens when marriages don't work.
Your spouse will push you to new limits, much like your co-founders would, and will keep you grounded like Anand mentioned below. I think the best pair of co-founders is exactly that - one realist, one dreamer.
It's been an asset to our startup: a married member of the team keeps us grounded and gives the company perspective.
Married people tend to be slightly happier than single people (not sure if that's hardworking happy or fat dumb happy), and as many distractions as marriages add, many distractions single people face get handled or eliminated by the other partner.
Startups are stressful places and marriages tend to reduce stress on average; I'd look at it as a very weak plus.
We live together, have a 10 month old baby and we're getting married in July. I don't think the marriage will change anything.
It's not particularly easy to spend this much time apart, but she's a champ about it. We would not be the same company without her.