Well, number of texts has never been an issue (for some reason it NEVER lags). Did not upgrade to OS 5.0 because I heard it had issues, but going between OS's in 4.6 is easy, from what I know you cannot downgrade from 5.0 to 4.6 so I'm using the latest 4.6, but it backs up all settings as well if I go from 4.6.x.x to any other 4.6.x.x. OS. Something I really like!
Even on WM's, the update process is not tricky, after using the tools off XDA Devs website (First time I **** bricks, but then became confident). Nokia's process is a bit slow. iPhone's probably the most idiot-proof. (Ever see Quickpwn's illustrated iPhone update-for-dummies? - I thought it assumed iPhone users on Mac were morons or something, and insulted my intelligence).