I have a similar router (WRT54GS v4) and have been very happy with it. All networking devices have their quirks, you just have to learn what ones your device has and how to fix it or work around it. If you are looking for more info about your router, you will be interested to know that your router is the same router as the WRT54G v4 with a different name.
The main known issue with the WRT54Gs is that they often choke when there are a large number of active connections. This often occurs if you use p2p software like BitTorrent but also occurs with other software.
The first thing you will want to do is upgrade to the latest Linksys firmware and see if that helps take care of your stability issues. If it doesn't, you have to option of running a third-party firmware like
DD-WRT, which is what I run. The third-party firmwares give you more options when configuring your router.
Even though I have yet to understand the reason for this, I have found that my router got more stable after a few days of running. Mine had a few hiccups for the first week of running but has been rock solid since.