I don't want to own any GM stock but if I were inclined to buy some, it would be after the IPO smoke clears. The price of recently issued stocks can be rather volitile until after the IPO action dies down. Give it a quarter or two and take a look at the financials after that to see if you still like the prospects.
If you are just a GM fan and not an investor then go ahead and just buy some. Ask your broker to deliver a certificate rather than register it in street name. You can frame it and hang it on the wall.
-Mark.