Lemme see.. in order to be fast, well integrated UI... Puffin will hafta..
1. Indexing

a) Background / Screen-saver indexing of your harddisk (boring.. )
b) 1-time indexing 'wizard' when installing (boring.. )
c) All of the above, plus newly created/updated files are monitored and indexed as per Anti-virus does.
2. Searching: Indexes will be several times larger than the content itself, so where are all these gonna be residing?
a) Google will host, so Puffin actually searches your indexes online (hosted by Google). So, your harddisk search will be as slow as your google search.. (*ringgggggggg* privacy alarms goes off) but that's still faster than searching for anything in your hddisk now!

Any bright ideas anyone?