So far no problems, wpml works just fine but you might wanna check this: WPML Compatibility thread - #20 by zestjosh
Overall I’d say everything is stable buuuut you might have to find little workarounds here n there and be ok with sprinkling some css here n there.
As for templating, I haven’t run into any issues but for some more specific cases, people had to find workarounds so if you do have a rather complex site, it might be worth looking through the forum a bit.
I say go for it but just keep an eye on client sites.
I’m using it on client sites but for now I’ll be the one doing the updates on a staging environment cause who knows…