Shift-clicking cards in play is sort of strange... Why not just have it as a right click? May not work in flash (Unsure) but would certainly work in the downloaded version.

Also when you scroll over a card, that card is displayed. Unfortunately, sometimes you need to drag your mouse over to the text to read what a certain ability does (Those with clickable blue text links). Sometimes, when the card is in your hand, this will cause you to scroll over other cards, making the initial card you were trying to look at disappear. Could this card-viewing system be modified so that you can click a card to view it in that panel, and otherwise it won't show up?