The speed you get depends on your own connection speed, and that of your uploading hosts, and if their speed is slow you can't do a thing about it.
Personally I have a 400 Kilobit (Kbps) connection which equates to 50 Kilobytes (KBps) but many downoads from a single host come in at around 5KBps.
Most hosts upload speed is slower than their download speed.
With more hosts, (you can get 8 in most set ups but this can rise to 14 if you have pro AND the fastest T3 connection) one will get increased speed, and this an important feature in Limewire, but I cannot expect more than 40-50 KBps and that is on a good day with my connection speed.
Stay clear of files with huge numbers of hosts btw, they are very often spam or worse.
You can download any file from this site
http://www.magnetmix.com/ and this should tell you what speed you can expect as a maximum.