Really clunky interface / doesnt work well

I tried this app ( under Yosemite ) as well as another app that pretty much did the same thing, it had real trouble logging in, it was tremendously slow, I have 24 gigs of ram on a 2013 iMac, my system is not slow, however just signing i turned into a 10 min ordeal. when I finally was signed in, the interface itself was so slow and clunky to use that it was impossible to use functionally.

drdata about Tab for Google Calendar, v1.0