Worst case scenario:  You have insurance with normal medicare assigned
to your insurance and you decide to get Medicare Part D through some
outside provider such as your local chain pharmacy since it is the
least expensive source of your meds.  Because you will be "double
dipping" as defined by Medicare, your assigned medicare benefits will
be cancelled and your medical insurance which was part of the package
will also be cancelled.  Your only option at that point is to rejoin
your medical provider at the normal, non-medicare assisted rates.  In
addition, if your insurance is provided through an employer with a once
per year open enrollment period, it is unclear whether or not you can
get back in before the open enrollment period comes around again.  Most
HMO's have their own Part D access and you could get it through them
with no penalties.  However, be sure to ask first.

In addition, not all medications are paid for with Part D.  If you have
two or more conditions typical of the frail, elderly such as diabetes
and hypertension, you are eligible but if all you have is prostate
cancer and taking lupron, you are not eligible.  And even so you only
save money beyond the donut hole which is somewhere around $2500.

I'm no expert on this stuff but I would think seriously about what
you're doing before signing up for anything related to Part D.  You
don't want to save $50 per month for medications (or maybe nothing if
your medications or condition don't qualify) and end up paying $1000
per month or more just to reinstate your insurance.

Beware when a government official says "We're here to help you."
Dave Perry