After few hours of playing with it I have these comments

missing games & integration issues:
- Epic:
Beyond Two Souls (not yet available to play, but it is in the library)

- Origin:
Command & Conquer Red Alert, Counterstrike and The Aftermath
Command & Conquer Red Alert 3 and Uprising
Dragon Age Inquisition

- Uplay:
Anno 1602
&
Splinter Cell Blacklist and H.A.W.X.2 games are missing the "Tom Clancy's" in their name

- Steam:
ARMA II: Private Military Company DLC
ARMA: Combat Operations
Deus Ex: Human Revolution Missing Link DLC
&
Drakensang marked as duplicate


issues:
- in activity pane, some games from other platforms have same day as "played for the first time" and e.g. "25 hours played" (3 days ago/uPlay), there are some others that have the same with "X months ago", but do not know if that is exatly to day or X to Y months

- some games don't have any media (maybe copyright issue)
SimCity Digital Deluxe Edition (Origin - no media)
SpellForce 2: Faith in Destiny Deluxe Edition (Origin - no media)
Ultimate Custom Night (Steam - no tile)


suggestions:
- separation of custom tags from the platform tags, if I hide any tags, unhiding the tag moves it to last place, so after some hiding/unhiding it could get messy

- to be able to sort tags (by name, by number of games)

- All Games and Installed "tags" have counters shown, it could be usefull to have option to have them shown in other tags/platforms, could be easier to check if some game is missing from the integration

- When you have grid format in right pane, there could be some icon/indicator to show the source, like it is shown in list format, so if you have duplicates, you know which one you would like to install/launch

- grey background on a scrollbar on the right is bit disturbing for me, I would like it to be in same color as the right pane