I'm a bit late on this thread but i'll chime in...
If you aren't on a tight deadline, or working with clients directly on your shoulder and your boss understands you need some time to grasp the DS, i'll say go for it. If you just know Xpress, maybe it'll be a bit hard to get up to speed with DS because timeline behavior and media management is pretty different. But doing effects (especially compositing) on DS is a charm compared to Xpress/Symph/MC. I came to DS from FCP/AE/Combustion and it was easier to get comfortable on the DS than later when I learned MC. I whish my job would make me work more often on DS than I am right now.... it's a sweet tool when you need to deliver quality products.
If you want to try DS, there is a "training" version you can download and explore at home on a PC with a decent graphics card. Unfortunately, it was recently updated and is currently unavailable, but you could email avid to get it I guess... here's the "coming soon" link:
http://aviddssupport.softimage.com/index.htm?section=documentation&page=DS_...
DS also has a Google List my many passionate and knowledgeable DS users:
http://groups.google.com/group/DS-List/
plus a wiki with many tips and tricks not in the manual:
http://dswiki.wikispaces.com/
