The long awaited 6.55 is finally out today with tons of changes including 2 new heroes and some new items. It is certain that the new map will cause an impact to competitive DotA scene, once it is implemented with some notable heroes and items nerf.

The New Loading Screen

Some changes that affect hero selection :

* Reworked Keeper of the Light
* Various changes to Enchantress's abilities                                                                           
* Rebalanced Insatiable Hunger
* Reduced vision aoe on Spin Webs and tweaked cooldown and manacost progression
* Reworked Call of the Wild stats and mechanics
* Decreased Watcher's vision a little bit
* Increased Sand King's armor a bit
* Lowered Chaos Meteor cooldown from 70 to 55
* Rebalanced Haunt cooldown (150/120/90 -> 120)
* Decreased day vision on Visage's Revenants by 400
* Removed magic immunity from level 3 Revenants and added improved magic resistance
* Rescaled Medusa's Purge cooldown from 12/11/10 to 12/10/8 seconds
* Reduced Chronosphere cooldown
* Ravage AOE decreased for level 1 and 2
* Decreased Guardian Angel AOE and duration a bit

Some notable item changes:

* Changed how Scroll of Town Portal works
* Reworked Black King Bar
* Aegis now respawns you where you died with full hp and mana but is undroppable and unstackable. Roshan takes it back when he respawns if it is unused
* Increased Guinsoo's Scythe of Vyse cooldown
* Reduced Kelen's Dagger cooldown from 30 to 15 seconds
* Kelen's Dagger now only triggers on player controlled damage
* Changed Max Stock on Observer Wards to 2
* Decreased Sentry Ward's truesight range
* Couriers can no longer place wards
* Increased Boots of Travel movement speed by 5
* Boots of Travel now takes the same time as scrolls teleport (4->3 seconds)
* Rebalanced tangos to come in batches of 3 (same overall regen per pack)

Other notable changes:

* When there is only 1 Assist to a Sentinel or Scourge kill, the kill is
instead given to that hero. When there are multiple assists to a Sentinel or
Scourge kill, the gold is split amongst those assisters rather than the
entire team
* Changed First Blood to be given to the Assist players when creeps kill the
hero rather than giving it to Sentinel or Scourge and splitting
* Tower gold is split if Sentinel or Scourge gets the last hit
* Denied towers give 50% team gold rather than 0%.
* Global team tower bounty increases a little per tower level
* Roshan now gradually becomes stronger over time instead of after death
* Increased Hero Kill Experience bonus a little bit (+8 unshared experience per hero level in an area)
* Hero Kills now give a flat gold bounty in an area (+40, not to killer)
* Lots of various terrain fixes and improvements
* Removed Crow's mana upgrade capability
* Revenants can no longer attack items

Detailed Item Changes:

New TP Scroll:
Any number of people can teleport at the same location at the same time.
You can choose the relative area around the structure that you want to TP
to.
Only allies see the exact position, your enemies see it on the building
only.
Does not give any bonus armor
If structure dies while you are tping, the tp does not force cancel
2 second shop cooldown
Available in Goblin Shops

However we have a new item to replace the armor bonus given by TP scroll as before.

Glyph of Fortification:
Consumable Item - Instant cast, does not go to inventory.
Cost: None
Cooldown: 6 Minutes
Stock Max: 1
 
Gives Old TP Scroll style bonus armor to all allied buildings for 4 seconds.

Finally the improved Kelen's dagger and balanced BKB. BKB's duration and cooldown decreases everytime it is used now.

Kelen's Dagger:
Only gets disabled from player based damage
Reduced cooldown from 30 to 15 seconds

New BKB:
80/75/70/65/60/55 seconds cooldown
10/9/8/7/6/5 seconds
Total: 3910

IceFrog and his team are trying to decrease the game duration by encouraging pushes and gank.

It is no longer easy to gain vision with the wards and flying courier nerf. Moreover, the vision of Broodmother's Spin Web, Visage's revenants, Weaver's watcher has been reduced, and even the Beastmaster's hawk has lost it's permanent invisibility.

This means that no more safe farm for carry heroes anymore and it will be another gank era.

Update: 6.55b released

*Fixed a critical error bug with Roshan as well as lots of other misc issues

Complete changelog