This appears to be a great plugin and has a lot of potential. As others mentioned, I had a problem with it crippling the entire site as well. It took about 7 or 8 installation tries to get it running 100% smoothly. If you purchase the pro version you have to install two plugins in a very specific way which I did each time....8th time is a charm?
The support that comes with Pro sucks. I've had a problem with a small part of and posted to their support forum. The first "solution" screwed up my site so bad I had to reset all the settings and spent half the day getting it back to where I had it. The second "solution" was to read all their instructions again. Which would be great but when you click on one page to the second page, find the specific thing you want on the second page, click on it and it takes you back to the first page. And YES I did read directions BEFORE I asked. There was NOTHING on there about anything remotely near my problem. And in the end, after 3 days of all this CSS code and creating and renaming PHP files, I quit and went into my Wordpess settings and with one click fixed it all.
There are better calendar apps out there, I suggest you find one.