There's a setting in there about "number of half-open connections" in the TCP/IP settings in Options. If it's too low, then you will be restricted in the number of peers you will connect to (I use a value of 50, vs a default of 10 in Windows).
It requires a reboot to change this value.
The downside is that you *may* notice a slowing down of IE/FF when browsing as the CPU has to switch between many TCP connections.
Supplement from 10/26/2007 11:14am:
PS - due to the technology, your download speed is potentially limited beyond your control:
a) if you have a suitably snotty ISP, they will throttle any P2P traffic
b) if you are d/ling "rare" files, your speed will be limited by the number of peers/seeds and the limits of their connections.
If, at the end of all this, you have dozens of peers sending traffic to you, but it's coming in at a trickle, then either they're all on pants connections, or your ISP is throttling you. You can potentially overcome throttling by using encryption, but that requires a certain amount of tweaking of your router (if you're using one) and I've never got it to work with Bit Comet. I've heard Azareus has good support of encryption, but I couldn't get that to work either - mainly due to my knowledge of router configuration being rather poor :-)
