I've noticed that users of LimeWire Pro are able to successfully access my files and complete the download more often than nonPro users.

I use LW 4.08 on a cable modem and OS X.3.5.
If i were to upgrade to Pro, would more non LW Pro users be able to access my files and successfully complete the downloads?

I don't think that that"s how it works. IMO, who connects to you and who doesn't involves a great deal of luck.
Then again I'm wrong about many things and chances are that I'm also wrong about this.
Let's see...
Maybe someone will enlighten us.

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-

We can't easily tell exactly what perks the LW team include with each release to give Pro users a bit of a boost. Maybe Pro users are currently given a longer timeout . . . ?

There are many ways to get an advantage, but most of them would be unhealthy for the network if EVERYone used them (like automatic requeries, longer timeouts before a query died, and many more). In fact, vendors are banned by major players (like LW) if these 'advantages' are used too often.

So, LW gives the smaller set of Pro users a BIT of an advantage, but not so much that it's really noticable or affects the network too much.

Forget the Pro "Advantage". Support the development of gnutella because gnutella deserves it and you want to see it continue.