Our official position is that we support all browsers supported by Salesforce.   (See their list here:  https://help.salesforce.com/HTViewHelpDoc?id=getstart_browser_overview.htm)

Having said that,  there are some wrinkles. 

The builder experience is not going to be very effective in IE 7 or 8.  
Tables with the new Frozen Columns feature will only work effectively in Firefox and Chrome. 

Hope that helps in your planning. 

That is what I needed.  Thanks.

For posterity - here is the page where we keep an updated document about supported browsers.

https://docs.skuid.com/latest/en/skuid/supported-browsers.html