Not exactly. There have been a number of security issues solved between 1.1.4 and 2.0.1. Using the older version constitutes a significant risk to the health of your system.
As to themes, the 2.x.x versions are significantly different to to the 1.1.x versions. There are a number of things, including extensions, that have not yet been upgraded to the newer versions.
BTW, clicking 'mark all upgrades' in Gslapt and then letting it execute with the test repo enabled exposes you to the risk of system breakage - that is why it is called testing. While it is something of a pain, I would suggest that you select 'mark all upgrades', click execute, check what is to be installed, and then use Edit > Unmark All, then select the items you want individually. Its a lot safer when dealing with test software. Its a pity Gslapt doesn't allow individual packages to be deselected - maybe it should be requested as a feature to the author.