I'm pretty sure nobody sees a bubble *ironic wink*, however I don't think this is relevat from a long term perspective. Whatever happens, I am pretty sure the price will be higher than now in 2 years.
Last bubble 2 years back peaked at around 30 usd.
There is a substantial delay, not everybody who wants to buy can do so, it takes time to set up everything (transfer cash to mtgox or everywere else), so the bubble doesn't even expand as fast as possible. I mean I'm desperatly waiting for it to burst, but now I think it might even cross 300 USD.
If you are interested long term, I'd just buy at regular intervals regardles of price. (i.e. 100 USD every week). That way you get the average price over the year