To round up the idea.
For a 3Com swith i was looking at today, they stated in their data sheet that the latency was about 2.7us in a store and forward architecture. the latency times you deal with is not very large, that is if you are only going through one switch, if you start bulding a larger network, latency is going to increase.
If you want more information on the amount of memory or the capacity of the MAC tables, you can check the switches data sheets, you con go to cisco or 3com or any other manufacturer for that, the state those features in their datasheets.
if you need more help, let me know, this actually seems like a topic i can give you a hand on, since i work for a networking ompany... at least for now :S...