How is it being dumbed down again? You can still buy apps elsewhere and you can still do everything you want like on Lion or Snow Leopard, providing that those developers keep releasing the apps outside of MAS.
MAS is optional and so is GateKeeper.
Once both MAS/GateKeeper becomes mandatory, than you can say "dumbed down" as well as "locked down".
That's a long discussion with many heated on both sides of Apple's focus on the consumer market while neglecting professionals. Since iOS development, OS X has been given less significance. This was apparent with Leopard being delayed twice as Apple OS X engineers were moved into iOS engineering for the iPhone launch. Having worked at Cupertino, and having friends still there, it hasn't changed. First affordable power systems such as PowerMac G4/5's increased in base price with the Intel switch in 2006. Apple once offered three CCFL LCD's that were highly regarded by the professional industry due to native calibration which negates the necessity for third party calibration devices such as Syders, anti-glare screens, IPS panels and offered 20/23/30" sizes (now replaced by a stripped down 27" iMac LED LCD panel marketed for notebooks and notorious for banding, bleeding and uneven colors, I went through 5 24" LED LCD's until I got one of my two that worked out of the box). Used to be a PowerMac with display would run about the same price point as a well equipped Mac Pro. PowerMac's didn't eat into iMac sales as it catered to power users and high end customers who need an upgradeable system that can be used with a display of their choice (EIZO displays have become the display of choice for many design professionals). Jobs even stated to a room full of industry professionals after acquiring "Shake" in 2004 that their input would no longer be needed.
Aside from professional hardware neglect, OS X has become more iOS in many ways. First, ADC memberships dropped from hundreds of dollars to the $99 annual fee as iOS. This was done to entice consumers into OS X development. Secondly, OS X engineering has been strained as Apple does not like to hire more engineers, instead keeping a tight knit group that can be moved between departments. Apple's surge in demand has surpassed its ability in development. Lion has demonstrated [comparative to previous OS X versions] that stability has suffered. Reading reviews and threads has shown an overall increase in customer complaints (and this is just general consumer reviews, ADC threads and bug reporting has increased, with bugs since Lion DP1 still open for many). HFS/Finder is in desperate need of a rewrite, Lion memory management is atrocious (the argument that should be fully utilized RAM is erroneous; my Mac Pro with 16GB DDR3 running simple apps such as Safari, Mail, Calendar, etc utilizes ~40-50% of my RAM, once I open Final Cut Pro X 10.0.4 that jumps significantly), lack of improved "Time Machine" functionality, poor OpenGL Core support (4.0 support should have been implemented long ago), multiple display support is suffering, carbon is still used in some apps as well as 32-bit core Apple apps, "Mission Control" is a great concept but was not well thought out and uses too many resources for iOS "eye candy", iOS Spaces is such a complaint that a developer, Steven Sykes, produced "ReSpaceApp", which has been such a hit that BinaryAge (makers of "TotalFinder"), bought the app - now dubbed "TotalSpaces", to reincorporate 10.5/6 Spaces into 10.7/8, and on and on.
Basically, consumer focus in OS X has strained an already stressed OS X engineering department, resulting in less stability and professional focus. Tim Cook recently stated that Apple will focus more social networking integration into iOS and OS X. While I do not mind iOS integration I do mind it at the cost of what made Apple such a great system, OS X.
