Yes, it would be nice.  I understand that SLA's are slated to be revisited in the semi near future, so there is hope on the horizon.

Sounds great.Beside the work days and weekend thing, I would even go further... The idea in my mind is that it would be nice to offer some sort of subscriptions regarding SLA. So based on your country / region you can e.g. subscribe to "German vacations" or "US holidays" or so, because every country / region has different holidays, national days, etc. and it would be REALLY nice in my opinion to have an option to subscribe to them, so that osTicket knows that for example the next tuesday is 4th of July and so it's not a working day in the US or e.g. that the next Monday is Whit Monday and not a working day in Germany. 

Ideally a custom holiday list would be creatable so that Organizations (in osT) and the company running osT could have independent lists.For example, Org #1-> Christmas-> New Years-> Independence Day (Mexico)-> Cinco de MayoosT Parent company-> Christmas-> New Years-> Martin Luther King Day-> Independence Day (US)-> Memorial DayThe system could then compare the two and discount those days that overlap, as well as take into consideration for closures of the Organization   I would think that days where both are closed the SLA shouldn't tick up, and then the osT provider could provide a determination if the guest Org's should count or not.

I agree, but when I read "custom holiday list" it shivers me a bit, since (we here in Germany) have days that change every year, e.g. Whit Monday and are not always at the same date like christmas. So it would be good to have the custom list option, but maybe there are cases where an automatism is better. Don't know exactly, so let's wait and see what the devs come up with and give feedback to them when we are there.

We here in America also have holidays that change their date(s) yearly.  But there is usually a pattern.... such as "Labor Day" which is celebrated on the first Monday in September.  Do yours also follow a similar pattern?  Or are you saying that we need a fleshed out calendar and Admins should be able to look at said Cal and make events?

Just needed to look that up myself on wikipedia Yes the follow a pattern... but it's not that easy. Everything relies on the Easter Sunday and is then e.g. 3 days before Easter Sunday or 49 days after the Easter Sunday and so on. So far so good, but now it gets a bit tricky... Easter Sunday itself is breaking the scheme a bit, because it's based on spring and full moon - totally weird, but that's how it is.Since I do not want to quote all the stuff, just read yourself over at wikipedia: http://en.wikipedia.org/wiki/Easter#DateSo as long as the dates for Easter Sunday are in the system, the rest is fine, but without Easter Sunday it will be hard (at least for German holidays) to follow a pattern.I don't think that's such a big problem, since you could implement it somehow, but maybe in other parts of the world there are also such "scheme-breaking" holidays which you did or I do not think of, so we here will have a look especially at this point when the devs revisited SLA and give feedback to make it fool-proof ;)