I had access to one of the special edition Jag XJ6s (it was not a Celebration) but one developed for a milestone in Jags history (can't remember which one! <img src="/forums/images/graemlins/smirk.gif" alt="" /> ).
The car was a nice GT, didn't handle 'that well' but was comfortable. I did have a few scary tail-out moments as it did like to waggle in the rain on corners and roundabouts.
Build quality wasn't the greatest and there were flimsy parts as well as electrical gremlins. The car also suffered from rust in certain exterior panels.
Don't really know if I can recommend it and if it was myself I'd be tempted to opt for an XK8 as they are better built and don't seem to have the same rust or as many build quality issues.
Hope that helps?