Make sure you get LW from the only official site:
Lime Wire » Download LimeWire
It's been my experience that the difference between the Basic version and Pro is more subtle and not a drastic improvement. It connects to more sources which should mean better search results and faster d/loads, but unless you have a pretty fast connection you probably won't notice much difference in d/load speed. It'll help if your searching for rarer files, but popular files will be on both.
If your having connection problems, it's better to sort them out with the Basic version because buying Pro isn't going to make them go away.