This guide is largely written for players who have been playing Easy Mode (EM) but wish to transition to normal play, but are having trouble doing so, or would like to fully understand the difference in mechanics and metagame between the two. The basic mechanics of EM are simple--you have increased gold gain, increased XP gain, and towers have lower HP. However, this disturbs the complex interaction between hero and item balance tailored for normal play, thereby altering the metagame drastically.
Mechanic: In normal play, you get 1 gold per second. In EM, you get 2 gold per second, resulting in players with lesser creep kills approaching twice the gold they would have in normal play, while players with more creep kills see a lesser difference between EM and normal due to the increased percentage of gold gained from creep kills. This is one of the factors EM-detractors often cite, as the increased gold gain marginalizes the impact of farming. In addition, at 200%, gold gain outpaces the 150% XP gain, thereby resulting in heroes obtaining powerful items typically at lower levels than they would in normal play.
Metagame Translation: Increased gold gain results in heroes precociously obtaining powerful items, often when their level has not caught up yet. Stronger items rarely seen in competitive games are in abundance here--players often finish the game with multiple high-tier items. This makes item-dependent heroes more powerful in -EM, but it keeps item-independent heroes just as strong. Combined with the XP gain boost, this means that the ideal lineup may contain multiple carries, or weaker, typically conditional carries like Chronos, and still succeed. This also downplays the importance of ganking--the gold and XP loss incurred to a dead ganked hero is not always worth the gold and XP loss incurred to a ganking hero that isn't farming.
Mechanic: XP values for all units are multipled by 1.5 in EM, including lane creeps, neutral creeps, and hero kills. Denies are worth a constant 36/18 XP (to melee/ranged heroes, respecitively) in both normal and EM modes--therefore, denying a creep in EM is actually stronger than a deny in Normal on a per-unit basis. Holistically, denying is less powerful in EM, because each creep that you don't deny gives a lot of XP, making it very easy for outdenied players to catch up. Theoretically, if a player is able to completely shut out another player in EM denies, he will have a huge advantage so as long as he keeps it up. This is quite unlikely, however.
TABLE Creep experience values for normal and EM.
Metagame Translation: Increased XP gain means that heroes with low starting stats but high stat gains like Magebane and Arachna reach their peak effectiveness much earlier and easier. Heroes dependent on leveling all their skills, like Madman, also get a huge boost from EM due to the ability to reach their maximum skill-dependent damage output at a much earlier time. Gank-based heroes suffer, as per the reasons specified in the Gold Gain section. Jungle heroes also suffer, as the amount of extra XP gained through the jungle cannot match the amount gained through lane due to travel time.
Mechanic: Towers are much weaker in EM than they are in normal play. They have reduced HP and reduced damage--this makes it so that creeps survive much longer, and are more effective in EM. Other buildings, including barracks, are the same strength.
Metagame Translation: Pushing is a lot stronger and a lot easier in EM. Because creeps spawned in lanes with destroyed barracks give less XP and gold, this is just as important as in normal games. On the other hand, because XP and gold gain are boosted overall, it's arguable that the net effect is still limited compared to normal play. However, this does affect the power of support and push heroes that choose to buy support and survivability items. By boosting survivability over damage output, as damage output for these heroes comes from spells, they can push with less opposition against late-game heroes than in normal play, as late-game DPS carries need to buy damage to deal damage, yet are vulnerable without survival items or enough stats from leveling.
EM mode is a caricature of normal mode in that it exaggerates, rather than completely nullifies, normal mode's basic principles. For example, laning and denying are just as strong of skills in EM, but they require even MORE skill than in normal play to utilize effectively. Ganking is effective, but only if performed EXTREMELY effectively. However, for all but the most elite players, this translates to a dampening of effective skill; ie., a player who shuts down a lane in normal play is likely to cause an effective 5v4 because his opponent was so behind, but that same player's skills are marginalized in EM because his opponent can easily recover, and other players have large advantages too. Because of the removal of the early game in EM, certain heroes who excel there have their effectiveness significantly lowered. This means that the peak effective times of each hero are drastically different--in general, for AGI, they become effective much earlier, while for INT, they become ineffective much earlier. The window of time for a mass healer/summoner push, for example, is much smaller in EM than in normal mode.