It may become an issue if at some point you decide to have kids - you may not want to raise them devoutly and he might...Just keep that in mind for the future in case the two of you get married.

Im an atheist. I dated a catholic guy for a while, and I thought the same you did: religion didnt matter. But the relationship didnt last, lets just say...I most likely will only date a non-religious person from now. And the pool isnt small at all, you will be surprise at how many atheist/agnostics are out there.

That said, YES it can work. But you both have to click and there needs to be a mutual understanding and connection for it work. PLUS, acceptance is key. If you cant accept his beliefs and cant see yourself accepting it long-term, it will always bother you and eventually it can create a drift (unavoidable).

#1: be honest with yourself.
#2: is he accepting of you too?

If you are trying to change him, and he you, then it cant and WONT work. But if you both accept each other, then it can.

I think that as long as you can respect the fact that he has made the decision to practice a set religion just the same as you have decided to practice a non-religious life it can work. If you disrespect or are close minded towards his beliefs or if he is dating you with the hopes of someday converting you I don't suspect it will.

I was raised catholic, and am agnostic now. Not atheist, because I see no proof for either a god or lack of god. The thing is, I'm still culturally catholic, you can't erase that much tradition and custom from me, I'd have no idea how to relate to my family if I suddenly abandoned everything that made me catholic. I also enjoy that I was born into something that has been around for almost 2 thousand years. I have friends who were raised orthodox that feel similarly, not everything about the older religions is about faith, it's about feeling rooted to tradition and history. Obviously I have met faithful Catholics who are very offended by that, and I respect that it may be insulting to some peoples faith, but I just can't help but still feel catholic even if I don't necessarily think there's a god. It's also a problem I've encountered with some atheists and agnostics, they think it's wrong to hold on to a religion if you know god isn't real, and that I should stop using it as a crutch and grow as a human being. Also valid. Except, it doesn't feel like a crutch to me, it's not that I go to church regularly, but I pray when my family prays, go to rosary's when friends die and just keep up with the traditions that bring comfort to my catholic friends and family. Also, I love candles and incense....it's superficial, but they smell so nice and I enjoy walking into a church because of it. Needless to say religion becomes a source of conflict between me and romantic partners, mostly because I'm either to religious or not religious enough for them, so it's rather refreshing to date a Buddhist. I respect him, he respects me, we don't talk much about religion, not because it's an elephant in the room but because our spiritual paths are rather different and personal.

Yeah, in the long run, the odds are not promising. Sorry to be a downer, but such differences in worldviews, religious beliefs, they're gonna grate on each of you. Especially where kids are concerned, you'll each want to raise them according to your values, which are very different from each other. It is possible, but rarely works, requires both of you, not just one, to compromise and be flexible.

I must say I didn't realize there was such a thing as a militant agnostic...

The definition of the word militant includes words such as combative and aggressive. I'm guessing if your relationship doesn't work out it will have nothing to do with the religious issue. The fact that you self-described yourself as militant in one area of your life can only make one think that you are militant in other areas of your life as well. One person being militant in a relationship would seem more like a romance killer than different religious views.