I dunno man. It changed the how, but it didn't really change the what. It changed how things looked, but did very little good with how you and the game interact. Aside from exploiting the build system to create things the game never intended, once you leave the game and actually simulate spaceflight, the only real improvement is the aero system.
Something the vast majority wouldn't have even known there was a difference if it weren't for patchnotes and update peeks.
Aside from that, 1.5 is a buggy and frustrating experience that you have to work around, awaiting the craft to split open like a supersonic banana or have all your fuel to disappear cos you used the RCS at the wrong time.
Which is my point. The previous update dropped and poof, you were gone. Not even a 'check out all these cool things I can do, it was well worth the wait'. Well, apart from the usual 'need more features' anyway.
How much did 1.5 change what you did in game, outside the VAB...?