Wanted to pitch in some thoughts...Am a long time user of Draft Dominator on PC, and I helped Beta test the Draft GM...on both iPad3 and iPhone5.
1. Was an Android user for about 3 years, switched to iPhone5 in January after getting hooked on iPad for casual browsing, reading, app usage. Have found iPhone to be much more intuitive, fewer problems, fewer 'bum' applications that are either not as designed or eventually completely lose support (or later are given away for free)!
2. What is Draft GM? It has the 'feel' of some of the better Mock Draft applications online...large Draft Board, with the ability to click over and see team rosters, rank players, create a player queue, and see VBD and ADP rankings of players (as well as click to Player news and Injury Reports). Use it to Mock draft or Manage a face-to-face league draft.
3. Draft GM Customizability (is that a word? anyways...): You can set Roster requirements (IDP included) and Scoring settings (right down to sliding scale PPR) and save those settings for your Leagues. It has the ability to add and save your entire League's teams, as well as keepers, and even switch around the Draft order (without having to re-enter the keepers! That was a pet-peeve of mine with Draft Dominator). You can have the Artificial Intelligence automatically pick for other teams during Mock drafts (and make the AI more or less 'smarter' for each team). You can manually enter picks as you might if you use it as a tool for your actual draft. Would be SWEET if someone hosting your draft has Apple TV, b/c you can transmit the output of iPad wirelessly to a TV with Apple TV. Also, another very nice feature: you can export and email the results of any draft in csv format, readable by Excel.
4. Draft GM Usability The 'draft board' lends itself much more nicely to the iPad. On the small bit of real estate on the iPhone, you can only see about 10 picks at a time (one round at a time). But, if you wanted to do a Mock draft on line at the Grocery on iPhone, go for it. I could see using Draft GM on iPad for ALL my mock draft needs. Easy to switch Draft positions of all teams and maintain keeper data. To me, that alone is worth the $2.99. I might also try to use it for my face-to-face draft draftboard (if can get someone to bring an Apple TV box).
5. What I will use Draft Dominator for even if I own Draft GM? : DDodds mentions it above, but Draft Dominator has more number crunching power behind it on PC, so has alot more data. I am pretty sure you cannot enter your own data / rankings for players on Draft GM, so if you are spending weeks preparing for your draft by customizing projections and want more than VDB and ADP at your fingertips, you need Draft Dominator at your draft
I could see using DraftGM for Mocks and maybe managing the League draft on draft day, but using DDominator to help drive my own personal picks.