Free vs Subscription vs Retail

Can anyone enlighten me on their experience of going from a subscription/retail purchase magazine to a free magazine? I'm contemplating this move in order to gain a larger distribution (with the help of a grant to cover the extra initial costs), but what about my current subscribers? I've seen several free magazines that also offer subscriptions...any thoughts? Will subscribers continue? Will they feel mistreated? The magazine will still only be available in select venues in select cities, so I can count on the fact that many subscribers will find it easier to receive it in their mailbox than go searching their city or another for a copy.

Any/all thoughts on this are appreciated.