If i download files from LimeWire from a Wireless connection (54.0 Mbps) and not plug in my ethernet cable, will this be slower than a wired connection?

I have a 512/128 broadband connection.

If yes, how much slower?

Could some also please explain to me what 54.0 Mbps is?

Mega bits per second. Divide it by 8 to give you mega bytes per second. So that equates to 6.75 MBytes per second. That is a lot faster than your connection abilities can cater for. 512 kbps = 64 KB/s (minus over-head loss in reality which ranges between 10-20%) which will probably equate to around 50-55 KB/s

Now ethernet speeds depends upon the ethernet cards in your computers. Normally 10 Mbps, but you can get up to 100/1,000 Mbps. I have all 3 on my mac but only use 10. I think the faster ones use different cable afaik. I'm not much of a knowledge on networking.

There may be other issues concerning wireless such as interference or distance between nodes. AFAIK All wireless devices have built in firewall such as NAT which is arguably a type of firewall. I can't remember much else about the ethernet speeds.

But I'm not qualified to answer your question about which is better. Wireless would certainly save you the cabling issue if you have the computers in different rooms, etc. (such as like mine are lol )

Thanks a lot Lord of the Rings. That put things in perspetive for me.

The only option for finding you if your wireless is as good as an cable connection is to test it out.

AFAIK if on your computer you get "Connection excellent" then there should not be any noticeable difference. Anything below that you will need to test by trying both with and without cable.

Concrete walls and similar obstacles have a habit of making the wireless connection drop to poor and then back to good etc.

In my case I can't use wireless for downloading (connection not good enough), but have almost no problems browsing the net and such. There is a concrete wall between me and my router.

BTW many wireless router have the option to change signal frequency which help a bit in some cases.