What's really made it a worthwhile investment is that it's given me a better understanding of language itself. All languages have idiosyncrasies, including Esperanto -- but Esperanto's idiosyncrasies are unusually consistent, making it really easy to map things onto. So I often find it easier to comprehend some weird construct in (say) Hindi or Japanese by mapping it onto straightforward Esperanto, rather than trying to map it onto an English construct that's probably even weirder.

Plus it's just such an easy win. I can order off a menu and find my way around town in a fair handful of languages, but haven't really gotten much further than that. But I can easily read just about anything in Esperanto, with 1/10th the effort that I've put into any other language. Which is just kinda gratifying to be able to do.

1: http://esperanto.cri.cn/

You can see some chinese uptake here: http://esperanto.china.org.cn/

Esperanto is very european in its appearance (both grammar and vocab). This seems to have helped it to gain a userbase, which allows others to adopt it who don't share its background. The regularity of the language helps people even if they have to learn a lot of weird roots and struggle to get the very latinate relative clause system (a lot of English speakers struggle with that too though, because agreement is moribund).

Esperanto havas parolantojn en Cxini, Japanio, Koreio, Indonezio kaj Tajlando. Nedube ankauw aliaj sed cxi tiuj estas tiuj de kiuj mi renkontis esperantistojn, aw en mia lando aw en ilia.

Jene vi povas vidi ion de la cxina uzigxo: http://esperanto.china.org.cn/

Esperanto estas tre ewropa law sia formo (kaj gramatike kaj vorte). Sxajne tio helpis gxin obteni fruajn uzantojn, kiuj instigas ekuzi gxin aliajn kiu ne kunhavas gxian historion. La reguleco de la lingvo helpas homojn ecx se ili devas lerni multajn strangajn radikojn kaj penas kompreni la tre latinan relativan fraz-sistemon (multaj angla-parolantoj devas peni per tiu ankaw, cxar konsento estas mortonta).