Our group just had an Email discussion on this today.
I too like the cards, but at 7th level, my Wizard had about 20 cards: 9 level, 1 racial, 6 class (4 cantrips and 2 bonus utility), and ~4 items. Even without being a Wizard, that's still 14 powers = 14 cards.
At level 20, that would be about 25 cards for a non-power intensive class, ~35 for a power intensive class like a Wizard.
That's too many for me to control effectively.
I saw a lot of card searching in our previous campaign. And, I heard quite a few comments from several players that they just plain forgot some option that they had when we BS after a session. I suspect it is too many cards as people get towards paragon levels for some people. So, I am going to use a descriptive list (or pictorial table). And, I can have an Excel spreadsheet auto-calculate changes as my PC levels.
And I can hand the list to the DM if necessary. Not quite as convenient as handing him a card, but still not too bad.
I think cards were nice at first level when we all started playing and they became part of the community culture, but I don't think they are the most effective solution. For one thing, they tend to hide options because not everyone lays all of their cards out at all times such that they can quickly glance at all of their choices. For those who do, it probably takes up quite a bit of table space, especially for old timers like me who need larger fonts, hence, non-tiny cards.