There are a number of things that LL could do - in my opinion - to make Prem Membership more attractive - especially for those who have been in SL for some time. The ability to use megaprims is definitly one - and even if there was a limit of say 30 or 50m to the megaprims it would still be a vast improvement to what we get today. Other things to consider are more group spaces, the ability to have more 'tags' or roles within groups, the possibility of adding tier in a more balanced way rather than doubling up all the time, the ability to keep more in your inventory (maybe this means penalising basic members), a reduction on upload fees - maybe 5L instead of 10L. I'm sure there's many more things that could be possible and not at a huge cost to LL - indeed most of the things I mention wouldn't cost them at all.