As a pro user, this'll make pro spawned servers more popular and so make me use the feature more often that Im paying for. Free users can still have the good old callvoting days by joining a pro-spawned standard server or as before by getting an invite to play on a premium one.
It adds value to the subscriptions which makes them more tempting for people to upgrade.
Sure it's a kick in the teeth for players who are used to getting the whole shebang for free, since they've now lost out a little but they still get a great game for free but with some added restrictions however they also gain the ability to access all of the maps from time to time.
Also for the people claiming that 'Quake 3 was free after you initially bought it' FFS the servers weren't free. With this business model, instead of generous people voluntarily running servers 24/7 that you could play on 'for free' it's now id who run the majority of the servers 24/7 - this change is putting it closer to how it used to be with id now running some slightly gypped servers whilst the majority will end up being run by community members. I'm 99.9% sure there will be pro users running 24/7 DM6 in no-time at all - all you need to do it befriend one and get invites (which using the greasemonkey script is as easy as getting on his friendlist and sending 'invite' as a message to them.)