1680's a great machine!
Rolands VS series are pretty incredible machines given the above mentioned learning curve. I presently own a 1680 and am wildly happy with the power and flexibilty of this piece of equipment. I've done several large projects and some small ones and have never been disappointed with the 1680's performance.
My only sticking point, and possible cautionary warning, would be that there is no good way, to my knowledge, to dump the 16 tracks you record on the 1680 to another device (i.e. computer, adat, etc.) and remain in the digital domain. The only way I've found to do it without going D/A/D is to dump the tracks two at a time through the spdif. This can be quite tedious.
This is not to say that the 1680 isn't perfectly capable of performing any needed editing, mastering, or other duty on it's own, because it is. I've rarely had the need to process outside the 1680, so it hasn't been an issue for me. The benefits of the VS series far out way any drawbacks in my book.