although I've found the net_applet to be reliable for wifi management, the signal strength shown remains at a low rate it picked up shortly after initialization.
I've also found that a tool such as Conky, which updates the current network status much more frequently, gives me a better feel for the current state of the network, including signal strength.
I'm sure the experts here will be able to confirm this and also give you hints at which tools can aid you much more.
If you find that browsing or other network activity does seem sluggish, then there's more reason for concern, but otherwise I'd just take a look at the upload/download rates. Simply right-click the applet and select what should be monitor network interface
(not really sure about the correct wording since I'm using a German version).
Hope this helps a little - and happy holidays