Does flattr complement or compete with bitcoin? I realise that the underlying technologies for Bitcoin and flattr are different, but do they serve the same purpose?

For example: if I set up a webapp that uses micropayments for revenue (like github - being able to buy private repositories) would it make more sense to use flattr or Bitcoin? 

Would I use them in concert - Bitcoin for micropayments, flattr for "charity" like payments for people who just want to support the site, but don't need extra functionality?

Does Bitcoin have a clear advantage over flattr for certain situations and clear disadvantages in others?
Flattr is a social micropayments system. Bitcoin is a currency.

There is no reason the two could not be integrated together, pay with bitcoins and then share the bitcoins out using the same method as flattr.

In fact, I would go as far as saying this would be an excellent idea due to lack of transaction fees and friction for small amounts.

Flattr is the service, Bitcoin is the currency. They don't compete; they could certainly complement each other though, in my opinion.