I downloaded LimeWire a few months go, and every time I open it I get a message asking me to update. Tell me, is PRO better? What adittional features does it have? I only want to update if it's worth it. Plus, can I TRANSFER my library or do i have to download all my tracks again?

Why would you ever need to download your tracks again?
Your tracks are stored in their folder as plain files that you can use with other applications and players. Even if you have stored your tracks in the default storage folder proposed by LimeWire, this folder will not be deleted if you install a new version.

And this folder will not be deleted with its contents if you uninstall LimeWire to install a newer version.

Upgrade without fear. You'll benefit of the new performance enhancements that are implemented in BOTH the Basic and the Pro version. Upgrading will also help others to find your content more easily, and will globally help the network to implement faster newer protocol features.

The only differences between Pro and Basic are indicated in the download page. But both use exactly the same networking core and the same GUI interface (the Basic will only have one additional area for advertizing if you use it, and it comes with an installer that proposes you to use partner products (these partner advertizing products are not installed with the Basic version and there's no requirement to use them as they are installed separately)

There's not any spywire in Limewire Basic, just a few ads... The main reason to buy Pro is not to have a significantly better experience, as the Basic version is equivalent, justed tuned by default to use lower bandwidth and slower searches, but still optimized equally with the Pro version so that either version will not take more than 5kbit/s when running in UltraPeer mode for sustained periods.

This means that you can keep your servent active permanently. Even for a temporary usage, you'll immediately notice the reduced CPU usage and reduced virtual memory swaps on disk if you use a PC with less memory. A lot of work has been done to improve the core performance, and such work is still ongoing with help of Beta-Testers, and Open-Sourcers that propose code patches or help improving the automated test suite that avoids any regression in the quality of the production releases.

Buying a Pro version or helping Limewire by becoming an Open-Soruce controbutor is the way to accelerate the developments, tests, debugging, support, and new research for new features, and to increase the interoperability with more non-LimeWire servents (to maximize your search horizon). The small fee for Pro is a contribution that also helps paying the support team so that they can assist you on forums like this one.

You are given the choice to make this donation, but there's no rationale why you should not upgrade to a newer version even if it's for LimeWire Basic, when you are informed to do so. See by yourself the benefit you'll get...

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Yes, You would be able to transfer your library over. Fore more info on LimeWire Pro click the 'Get It Now" link in my Signature. I hope this helps.