Interface: DraftDay just recently updated their interface to a much more modern version. To compare, it basically went from a Nintendo interface to an XBOX 360 interface stylistically. The new update is hard to get used to at first, but very customizable once you figure out a basic knowledge of the site.
Salaries: DraftDay is getting quicker and quicker about updating their salaries to reflect recent developments. They still only do a full overhaul about once a month or so to fully correct any obvious needs that are not addressed by their live updating salary system. On the bright side, intelligent players can take advantage of certain salaried players until those manual updates are made to correct them.
Competition: Currently, DraftDay is filled with new players because of how new the site is. However, there are players who have established themselves as mainly DraftDay players and know the ins and outs of the site better than most. Make sure to stay aware of the players that are sitting in every game at certain levels and do your best to avoid them.
Variety: Draftday is the cream of the crop when it comes to game variety. They offer just about every game the daily fantasy sports arena has to offer at this point. Hit It and Split it was their biggest development last NBA season and they have also introduced an exciting Jackpot game during baseball season that they will likely carry over to basketball as well.
Promotions: Draftday runs tons of promotions through both their Facebook and Twitter feeds that reward dedicated Draftdayers with free entries and bonuses for following them on the social networks. They are also one of the sites that first introduced the daily freeroll and they run one for every sport.