Bought a 1.52 Eur and upgraded to 2.00, then downgraded to 1.50 (had fun for a while but homebrew was still in it's infancy); Upgraded to 2.60 to play some games and then downgraded back to 1.50 and started to mess things up :)
Used the first "proof of concept" by dark alex and: eliminated umd autoboot at the start and initial sony logo, set Irshell as OS by using the autoboot at the start, placed DevHook and A LOT of emu and games like good old quake.
Planning to buy a 4GB MS once price drops dramatically.