Those are very difficult questions to answer. Much of it is based on opinion
and your own personal situation.
Are you in a corporate environment or are you a home user? If corporate,
Office 2007 could cause problems with non-2007 co-workers. Office 2007 uses,
by default, a new file format. Older versions of Office can read it but will
have to download/install a converter first. However, you have the option of
saving files in the older format. Even if you are a home user, the file
format issue still applies if you share documents with others.
The new ribbon interface is much different than you are used to. It will
take some time finding where MS relocated some functions. If you are patient
and willing to invest time to re-learn, you'll be OK. If not, you may find it
annoying.
So, the answer to your first question is "yes" and "no." Not very helpful
for you, but that's the way it is. "When will you suggest I move to Office
2007?"...that really can't be answered definitively. Perhaps you didn't word
your question the way you meant to. Regardless, you'll just have to try it
for yourself and draw your own conclusions. There is a free trial version you
can download from MS.
Tim