I don't think you can fairly compare, without a value judgement, this phone to new android models that run a more recent version of Android with better specs but cost $200 plus contract. The charm can be had for less than $100 on ebay without contract. I think the battery is ok if you run tasker, advanced task killer, and monitor your wireless connection.
This phone has flaws. GPS is bad. I am annoyed by the inability to run apps from the sd card, and some apps I have to track down on the web because the market doesn't display them for the charm. And while not all apps look quite right on the charm, not enough apps look off to offset having a tactile keyboard and paying $75 on craigslist for it.
I am not as familiar with the aforementioned complaints like bluetooth transfers so if those concerns are deal-breakers, then don't get it. But if you are looking at ways to save money and avoid getting locked into $80 a month contracts, then this is an option for you.