Yep, I did that - but they have three cons Im not fond of:
1) More costly (not by much but still)
2) Only come in one flavor - as in - they could only be gold or platinum.
3) They don't look as nice (my personal opinion of course).
Having said that, utilizing those as opposed to doing in-game conversion rates will only get so far - you'd cut down costs, but ultimately not enough to make me want to use them =)
If you stray too far and go for a 1000-point conversion (or use the new packs that actually have a 1000-chit in them) you would end up handing out very few coins, which isnt exactly epic. Of course, you could mix in change, but then you get into the whole "then I need to buy the change" scenario.
Its tough - because on the one hand you have the game in which items worth tens of thousands of gold are not THAT uncommon and on the other hand reality, where the equivalent of one chit costs around 0.5 USD, so if you want to average that out, even with a 100 value PP, you would end up having to pay hundreds of dollars (even thousands if you really wanted to dedicate enough resources to it) to cover a long-lasting campaign.
That said - the prices I listed above are for the campaign coins only, and adding in one of these packs: http://paizo.com/store/gameAids/other/campaignCoins/v5748btpy8g5a
could certainly help, but the bigger numbers you hand out, the more you need to fill in the space between those numbers (as in: you would need change for a 1000-chit if someone decides to buy something worth 334 gold).
Dont get me wrong, I love these things and would love to use them, but I much rather track it on paper at the end of the day =)