IMO these extensions hardly qualify as 'investments'.
Investments should have liquidity . Stuff that is not in demand is not liquid. It may be more a liability than an asset.
As always, look at reported sales, see which extensions and types of domains do sell and how often.
You need to do your homework, also keep in mind that the people pumping a particular TLD may have a vested interest or simply be subjective.
You're saying 'I have come across some good keyword domains', I guess you are talking about domain names that are available. If they are still available, you need to ask yourself why.
I think that in 2012 it's very difficult to make good money on regfee domains. You need to look to the aftermarket/drops, and allocate your budget toward domains that are already worth something
today, not in some remote and unlikely future. Raise the bar high enough: solid domains, solid extensions. Fewer domains but high-quality.
But maybe I misunderstood your actual intentions
