Replaced a flaky iPhone 4 home button - gave the phone a new lease of life and meant I don't have to buy a new phone this year. Spent $15 in parts and two hours in time and saved myself $500.
Went alright, not too bad. A few hickups like forgetting to ensure the screen ribbon was pulled all the way through before tightening which meant going through the disassembly twice, but second time round was much faster.
Have your screws lined up in order of disassembly. Be careful not to hold them too tight or apply too much pressure picking them up. They have the tendency to go flying like tiddly-winks.