Well, not sure where the rifled barrels are, but if they are on the Vipers, that could be because they are meant for atmospheric flight as well as space flight, so they would need to be accurate there.
I don't mind an updating of technology and stuff. I always applaud using more realistic physics, that isn't what bothers me. The combat and stuff looked cool in the stuff I saw, it's the other things that I found bothered me. In several reviews they comment on #6's spine glowing when she's having sex. Now how lame is that? Not exactly something you would expect to see in modern sci-fi. More akin to some of the old corny stuff that is unwatchable. Doesn't Baltar notice? I mean, really.
I also agree on the reason for changing the sex of the characters. I dont' mind changing Boomer that much. He was a supporting character, but I must agree that the reasoning for changing Starbuck seems pretty flimsy. If they really wanted to go through that male/female dynamic, there were characters from the old series that were female pilots after a while, and I wouldn't have any problem with that character being a capable pilot right from the get go and having a larger role.
I think my biggest problem with bullets in space is the amount of cargo space supplies would take up. Where do they store all the ammo? What happens when they run out? Can they reasonably hold enough ammo to stock all those fighters for battle after battle, as well as all the ammo for the rail guns, etc. and still have room for all the fighters, support equipment, etc.? They are making a huge journey, now if they make that part of the story that's fine, but I bet it ends up being more of a Voyager thing. They have unlimited unless someone wants to tell a story about it early on, but it will quickly become a non-issue (and it would certainly be interesting if all the alien races they come across used the same size/shape/type of ordinance, wouldn't it?). I'm all for being more realistic militarily, but the lack of computers on the bridge for some things "because they don't allow networked computers onboard military vessels". Well, what about non-networked ones then? Probably more effective than a grease pencil, I would imagine. What's with corded phones everywhere? That's certainly not modern tech, even for us, is it?
Anyway, my biggest beef is with what's been done to the story overall, and the characters within. I still look forward to watching it, but at this point, from what I've read, I think a different direction would have been better.