My primary goal for Shrugs wasn't better memory efficiency but a better user experience (i.e. using native controls, having multiple windows, quicklook, etc). It uses quite some memory because it does (too) aggressive caching and prefetching of messages (I have enough RAM, fast access was more important to me).
It is worth noting that the official Slack app has gotten massively more memory efficient about a 1.5y ago, its bad reputation comes from the time before that (when it easily used more than 1GB of RAM). (I think it still has other performance issues, but they aren't as big anymore, it is doing quite well IMO)
Having said that I'm working on improving memory consumption in Shrugs.app - it is a tentpole feature planned for v1.1 (it'll take some time until this will be ready though).
It is worth noting that the official Slack app has gotten massively more memory efficient about a 1.5y ago, its bad reputation comes from the time before that (when it easily used more than 1GB of RAM). (I think it still has other performance issues, but they aren't as big anymore, it is doing quite well IMO)
Having said that I'm working on improving memory consumption in Shrugs.app - it is a tentpole feature planned for v1.1 (it'll take some time until this will be ready though).