Yes, Go for the 245, but I would like to know the model of the mobo and the other peripherals you already have since that is what is going to last you for the next 3 years.
The AM3 is , agreed, reverse compatible with the AM2+ Socket boards but the rest of the stuff is what causes the main hiccups like the RAM the HDD the Graphics card etc etc and lets not forget the heat output.
For general purpose?? It's a relative term but I take it as functioning mainly on the net and word, excel, power-point. A little bit of low end gaming and some normal hifi music listening.
The 245 would be a great buy for that kind of usage.
Yes, you can upgrade to an AM3 socket board to get the full usage of the new processor after a year, that would be a nice idea and then the year after that you can change over to DDR3's making it a completely new PC. And hopefully by then the DDR3's would be dirt cheap so it's a 100% win to get the 245.
By that time I guess The Fusion and the Bulldozer would already be out and for all you know, they might be backwards compatible with the AM3 sockets.....