My experience of using SmartBro is pretty good - I have invariably found it faster and more reliable than the o2 equivalent I carry as an emergency back up travelling in the UK for when I can't find a McDonalds!!
That said some internet forums give it a slating for reception quality. If possible try one at the location in QC where it will be used. As I said I have had no problems in Metro Manila or Davao.
You do have to have a separate Smart mobile account, but pre-paid is fine.
To my surprise it does not block use of Skype - which is a major plus point.
Re the charging mechanism IIRC it works in half hour blocks on the hour & half hour. If you time it wrong you can pay for an hour and use only 2 minutes!!
Finally there is a supplier on ebay who sells top ups. They email the code immediately on receipt of payment.
