I've been really happy with OCC (OnlineChatCenters). Goofy name, but it just plain works. Took me a while to get used to hosted (though we migrated to hosted for a reason, and away from LiveZilla that we used for years), but it works well, very quick response and light resource usage, and is very reasonably priced.
In WHMCS it was relatively easy to set up a connection between the LiveChat transcripts (a new support department) and WHMCS. I'm assuming it will be the same with Blesta. You don't get the full intergration as with Stardevelop, but you get a much better Chat system IMO.
