Library Journal has picked up UTC's early adoption of the OCLC WMS. (As a fun aside, they also linked to both my & griffey's initial posts on the topic, which made me smile.)
We are going like gangbusters, with our ILS administrator running on popcorn and donuts as she does dark-hoodoo data munging, Griffey managing various aspects of this enormous project, various smaller area-driven implementation teams handling their business/planning and reporting out both to the larger implementation team and the library at large, cleaning data, and more.
I've been able to get my hands - or, more accurately, brain - into some areas I've never fiddled with before. Circ and lending policy matrices for the wireframe; not only which patron records we actually want to move over, but which *parts* of the records, and trying to standardize freeform notes; dealing with home locations, shelving locations, temp locations, and more; trying to reduce the number of patron-types we have; the dark mostly-unused corners of things we'll need to test. How I would integrate services and accounts and information if I could blue-sky things. Thinking about things from the user-side in terms of accounts and information. Chairing the circulation & course reserves implementation team has me waking up at odd hours thinking "OMG did we think of that??" - which someone inevitably has, or "Ooh, what about scenario Q sub-point four?" which always sparks interesting discussion.
Random thoughts: after looking at our free form notes fields to date, the idea of trying to run a report or munge data out of free-form makes me want to barf. Misspellings, word-order issues, synonymetry...humans - and circ staff - are nowhere near robotic enough to make that work well. Get to know the preferred pastry poison of your ILS administrator/IT team - it'll make you feel better when you can't change their Access database files into XML, but can give them an icing-filled donut. "WMS" is not sexy or fun - OCLC should name the cloudware something spiffy and give it a fun icon. There's an edge case for everything you can think of.
Everyone is running around crazy, but there's no panic-feeling (or at least not as much 'frantic' as you'd expect for a 30-day implementation of an untested library system). Getting into this sort of crazy with a bunch of folks who have a good sense of humor, common paradigm for service, generous spirits toward each other and an appreciation for the work others do - even if they know little about it - probably makes a hell of a difference.