My limited experience...
I have only been playing NL25 and NL50 for about two months. I always sit with max possible for the same reason as Chuck...never want to be caught with a smaller stack when I get the big hand. Yeah, I know, I can also lose more when I have a bigger stack, but that only concerns me if I am a losing player. So far (knock on wood) I am winning, therefore, I expect my bigger stack will help me in the long run. I also buy back to max buyin if my stack falls below 80% of max buyin. I have found that this works well for me.
I don't use my stack as a tool when playing cash tables. Maybe I should, but I find that just playing a solid TAG game has paid off. Also, at the low limits I play, I don't think there is any table image problem with buying in at max (probably 75% do the same). Actually, I don't think having the table image of a high-rolling bully at the higher limits would be a negative. With a TAG game, you may get calls that pay off well for you...so the big stack could be a positive.
So, I am curious what others think and how much the limits affect this thinking. Maybe it makes more of a difference at NL400.
BTW, I never understood the idea that a big stack is just someone you can double up through...they are also someone that can bust you! I know there are some who like tangling with the big stack, but personally, I just treat them like everyone else at the table (until I get stats and notes on them).