I had to import a lot, really a lot of data, more detailed - tracks, that means polyline data!
No other maps plugin even ofers the possibility to import csv data into the db, in my case, it didn´t work at the beginning (cause I had polylines, not single markers), but then I had luck.
I just wrote a support ticket, and got a really fast response. To fix the issue (which wasnt caused through bad coding, just my mistakes) there was a lot to do. An awesome guy called "Nick" helped me through that all, he even edited some files for me, and send them to me, a lot of work just for one customer!
That whole process took over 2 weeks, 2 WEEKS support and coding just for my special need, for free - just because he´s a nice guy and wanted, I quote :" I want that to work a 100% for you, so we will try on until it will work"
That was the best support I have ever got!
In addition to that, the plugin is really nice. You can easily import data, and even export it - thats a huge feature if you have a lot of data!
I recommend to everyone, invest the 14,99$ for the pro version, you wont regret!