Now it would be very cool if i could see in the deck which cards i own and which not. (Maybe Green = available; Yellow = Available but not enough; Red = Not available)

Such as Duel Decks Foil cards. Add those foil cards.

Geoff suggested: By the way, can you guys please create a video tutorial of how to use the client? I’m sure there are easier ways to do some of the things I do.

If an user is trying to add a card to the deck (either from button or drag and drop) and there is no deck opened to ask him whether to create such one for him.

Write a taxonomy which parses the card rules and creates the abilities automatically. Assign all abilities to all cards.

RR: What i'd really like is for a new field labeled "available" and it's value would be Difference of Qty field and Used field(Qty-Used)

It is very common you don;t have permissions to write to your configuration folder. Try to write to it on MTG Studio startup and report error if not being able to.

Would it be possible to include a price conversion process (Dollars to Pounds; Dollars to Euros) considering how much of a worldwide game Magic is.

Be able to previe the cards drawn instead of being displayed as text.

Allow to choose a checkbox "Exact Match" which will filter out other editions and foilness results and leave just exact card matches.

Add support for the set Mirrodin Pure VS New Phyrexia. It is currently suported in MTG Online.

Add support for importing collections from Magic Card Database software.

Add cards in their localized version as in Gatherer.wizards.com

Deck Strategy is currently calculated only on Open Deck - add it to the Deck Statistics as well.

I would like to be able to decide which (left) columns are fixed and which (right) columns will slide.

Add Planeswalker format - http://www.wizards.com/Magic/TCG/Resources.aspx?x=magic/rules/planeswalker