I've been using Lion since the first DP1 as an ADC member. At first I was impressed, but now that 10.7.4 beta is out, I'm unimpressed by the overall OS. I did a little experiment to compare "Snow Leopard" and "Lion". Setup: 12-Core Westmere 2.66GHz Mac Pro 16GB RAM 1 OWC 6G SSD (partitioned in half, "Snow Leopard" and "Lion") 4 2TB HDD's 1 LG Blu-Ray burner ATI Radeon HD 5770 2 24" ACD LED LCD's I installed "Snow Leopard" and "Lion" on their respective partitions (10.6.8 and 10.7.3), with the exact software, applications, etc. for both systems. Everything is equal aside from the operating systems themselves (both clean installs from a USB drive with all updates). All settings are set that can be across the OS aside from new features in "Lion", most of which I disengaged. Results: - "Snow Leopard" blew "Lion" away. Boots up in 4-5 seconds from the Apple logo's first appearance in "Snow Leopard", 30 or more seconds in "Lion" (checked both the main and home /Library/ startup/launch agents/launch daemon's folders and they were the same as are both login accounts startup items in "System Preferences", also checked that windows did not open in Lion by manually closing everything down before reboot). - Using "Blackmagic Disk Speed Test", my "Snow Leopard" volume averages ~250 on write and ~275 on read (OWC 6G 250GB SSD, and my Pro isn't even a 6G system). I barely broke the 200 mark in "Lion". - WiFi: In "Lion", since DP1, my WiFi speeds would drop over time. First they'd reach ~20 Mbps download and ~3 Mbps upload, 15-30 minutes later would drop to a crawling 2-3 Mbps. "Windows 7" and "Snow Leopard" have no issues with my WiFi. (checked my current gen AEBS firmware and modem, all set) - iStat Menu's - Running Mail, Calendar, iTunes, Safari, and EyeTV: - a steady 25% RAM usage in "Snow Leopard" - 40%-45% range in RAM usage in "Lion" - "Snow Leopard" does not have a ~10 second gap when logging in and loading login items from cold boot as does "Lion" (always has, no matter how many clean installs). - Geekbench 64-bit Results: - "Snow Leopard" 22549 - "Lion" 18340 "Snow Leopard" performed better in "Memory" and "Stream" - Application Loading: "Snow Leopard" loaded MS Office 2011 Word/Excel/Powerpoint, iWork '09 Pages/Numbers/Keynote in no time, barely a second, while "Lion" hesitates with some apps loading 15-20 seconds slower. "AutoCAD" 2011 loaded in no time on 10.6.8, took twice as long in 10.7.3 One aspect Lion handles better seems to be in multi-core/threading. I noticed some apps tax the first core heavier in 10.6.8. I performed these tests numerous times in various situations, hands down "Snow Leopard" beat out "Lion". Even my ex-colleagues who still work at Apple have commented on "Lion" being a memory hog and numerous complaints about its overall performance (many Mac enthusiasts have complained specifically about "Mission Control" and lack of "OpenGL" development in the current OS X). I, as well as numerous others, have filed many bug reports with Apple engineers, to no avail. It seems the focus of consumer level iOS feature integration has taken focus away from overall stability and performance in "Lion". As well, some consumers who are new to Mac's from the iDevice market do not believe the iOS integration simplifies the system as it isn't a true iOS experience and to some "feels out of place". Apple would be wise in listening to their customer base. "Lion" sold well as it was inexpensive and the only "OS" shipping on new systems, and with higher Mac sales of course the figures would report greater "Lion" usage. Next, "Mountain Lion" DP 2 with 10.6.8 and 10.7.3.