I get the feeling that we're losing the impact of "3d6 in order" when we start adding so many bonuses to the stats.
A high roll is supposed to mean something, but the more other characters can add to their stats then the less value there is in that lucky roll. Or, players no longer have to work around that weakness because given a little experience they can just add to that stat and make it go away.
One thing I love about the playtest reports is that folks are always mentioning some character who they thought would be lame but was a blast to play. A character with a low stat that added some quirk to the character.
I'm not saying that there couldn't be any plusses added at certain levels, but some of the ideas posted recently give as much as +6 in nine levels. That's faster than 3E!
I agree with your last statement. As I stated, now that I know you can reward luck after each adventure I definitely think this needs to be on the lower end. I am thinking they can roll for a chance
at a +1 every 2, but more likely every 3 levels. Most players will fail these rolls at least a few times so in the end you are looking at about 2 or 3 points on average. And since this game stops at 10th level it's not going to reach 3e ability levels.
I don't agree with some of your other points (assuming we use a lesser reward system like this one) though I do agree they are VERY valid concerns. The problem is it won't be until 2nd or 3rd level that you even get your first +1. If that somehow reduces the impact of the 3d6 by all that much I would be highly surprised (most characters and campaigns never even make it that far either). At 4th or 6th you might, remember this is not guaranteed, might have a total of +2. For most of the characters I have seen this still
isn't a big deal though, hardly noticeable. Let's assume that maybe you start to see a difference by 8 or 9th level, is that really an issue though at this point? You are supposed to be heroic level by now, fighting dragons and demons and such. You are probably still worse than a character rolled using 4d6 so you aren't even close to anything seen in 3e. In fact since most of us played even old school D&D with 4d6 the character will still probably look a bit gimpy to most of us.
And it's clear people are having a blast with these lame characters in one-offs but that's probably the novelty of it and I have some doubts about their appeal long-term. That's the whole point of this. They are fun right now but some of us have doubts about their appeal in long-term campaigns, not because they aren't super heroes but because I know many players will eventually get annoyed by the negative modifiers they have from low scores. You see it's not that I want characters to get 18s, I just don't want them to have 6s their whole career. That's why I will make my players roll over their scores. If you have negative modifiers it will be easy to boost your way out of them. If you are already "heroic" you will have a hard time ever increasing them. And if you are really lame, well even with the boosts it won't make a big difference.