Yes, it's enough. Poor performance will come from things like poorly constructed websites (too much JS, very chatty sites and apps loading resources across many domains, or calling home a lot, especially with limited upstream bandwidth), contention with other users of the connection, and latency (not often a big issue with wired connections). On latency, this piece from 1996 is still worth a read: http://www.stuartcheshire.org/rants/latency.html.