Moral of the story, bury hatchets (if only for a day), and bring a gift, even if it is a trinket. And don't walk in after the ceremony is over and then comment, "well these things NEVER start on time!"
I'm with you on burying hatchets (certainly don't make the bride and groom suffer due to things their parents/relatives did/didn't do). What a tradegy to miss out on Uncle Bob at my wedding because he is on the outs with Cousin Randy. what does that have to do with me???
Bringing a gift - not with you on this.
First, gifts should always be shipped to the home if possible. Bringing a gift is fine, but far easier on the wedding party to already have it at its destination so no one has to mess with it on the big day.
Second, a wedding invite is not an obligation to buy a gift. Invites should never contain info on where a couple is registered (no matter how popular that custom has become, it's tacky and presumptive). People should not feel compelled to give a gift, they should give a gift if they are so moved to do so. A card expressing good wishes is always good, and a fine substitute. If you want to put money in it, go ahead.
this is all my opinion only, not really sayign what anyone else should or shouldn't do (realized it sounded that way)
Being late? crap, it does happen, more often than I'd like to admit (last weddign I attended, teh church address was wrong, did not exist! the wedding did start late because some of the wedding party did not get there in time due to this fun quirk)
But if a person is late, quietly observe whatever remains, and keep your snarky comments to yourself. The bride and groom planned the day to go a certain way, guest role is to go with it, and do the best one can to get there on time and be a good guest (which means not complaining that the dip isn't very good, drinks are watered, or whatever. shut up and be a part of their special day, it ain't about You)
I hate being seated at a table with complainers, as if the event should have been designed to make them happy, and to hell with the marrying couple ...