I find that occasionally Entorage seems to run slowly. It slows down and appears to not be accepting input as I'm typing, then it catches up. It can be a bit weird in that c - h - a - r - a - c - t - e - r - s appear to slowly appear. It doesn't happen that often though.
Generally it's fine and I wouldn't let it put me off.
It will be wonderful when there's a genuine competitor to Entourage. Using iMail, iCal and the contacts database seems like going back to the days of the email app with Schedule+. Yuck!
The biggest issue with Entourage is its lack of support for PST files. This is totally dumb on the part of MS. I ended up having to install an exchange server just to move the data from Outlook to Entourage. Stupid, stupid, stupid.
Finally I did have a Mac crash that killed a Werd document. Werd/mac refused to open it. Fortunately I could open it on a PC and it fixed it. That was the first and only time Werd on the PC has worked better than the Mac. Normally Werd/PC will die after you have a complex document of about 30 pages (I regularly edit a particularly complex exercise manual for some courseware). Werd/mac is fine with even huge files.
One last thing, you can't edit in-situ PowerPoint slides in Werd/mac. I tend to embed a PowerPoint slide as a picture - I've done this for years on the PC and have to unlearn it on the Mac.