Why is it that some people really really hate interleaving on their DSL lines? Gamers are one well-known group. Is that all though?
Its simple really.
RTT is a key factor in performance, for most use cases its more important than burst speed.
e.g. a 10ms 10mbit connection for most things on the internet will offer smoother performance than a 100ms 100mbit connection.
a DNS lookup requires at least 2 x RTT to get a result back to the client. A website could easily have a dozen DNS lookups.
Establishing a connection to a webserver, again multiples of RTT before you even start downloading data.
Streaming will ramp up to higher throughput faster when RTT is lower.
Things like FTP where every command packet has to be acknowledged speed up significantly when RTT is lower.
Then there is of course gamers twitch shooter gamers are hyper sensitive to latency.
Where its not so important and burst speed becomes king is things like bulk downloads, so steam downloads, PSN downloads etc. Although RTT can still be a bottleneck if RWIN is saturated.
Very low burst speed like adsl1 speeds will be a bottleneck for various use cases, so my above post is assuming your burst speed is already at least about 15mbit.