Browsing is slow but not that unusable. firefox-esr is in the repos; I prefer palemoon but I'll take what I can get. Gnumeric is faster than LO; both are in the repos. The Broadcom blobs for that Gateway machine are sadly out of date, so I yanked the wifi module out entirely; ethernet works fine, though in most cases I use it landlocked. The editor I prefer (jstar) is TUI, so I mostly work out of xterms.
Use-cases? Remote and while-you-wait work, RS232 and ethernet test console. It's bigger than a netbook but it's what I've got, so I lug it around.
Not OP but I had a Late 2007 Core 2 Duo with 4G ram that could hold its own 3 years ago.
It was not comfortable but definitely usable (unlike a 2005 Imac G5 for example).
A 2013 4th gen i5 laptop with a SSD (major difference in trems of experience) and 8GB Ram remains totally usable for regular stuff (watching movies, Youtube, browsing the web, basic dev work)
The plastic body is generally what fails before everything else.
As long you have at least four cores, 4GB Ram, linux and above all a SSD you should be fine
Use-cases? Remote and while-you-wait work, RS232 and ethernet test console. It's bigger than a netbook but it's what I've got, so I lug it around.