From Mavericks to Yosemite

I hesitated for a long time to to upgrade my 'old' MBA, vintage 2011, mostly because of the WiFi problems reported. But now and then I had Wifi problems using Mavericks too.  At my location there are a lot of WiFi routers on the 2.4 Mhz range, that reduced my speed  in my workroom seriously. My Linksys E4500 can do 5Mhz too, but my MBA couldn't connect to it. It seemed to think my router had a country code GB. My iPhone has no problems using the Wifi at the same location. Restarting the router didn't help.

So I decided to try. My WiFi problem couldn't get worse... Of course I first made sure my Time Machine backup was up to date and I made a bootable backup using SuperDuper. Make sure you have an external harddisk available with a HFS+ partition big enough.  I added an extra partition to my 1 Tb harddisk,  using GParted, booting to GParted Live using my old Windows laptop to boot from USB.  The backup will overwrite all the content, so make sure you use an empty partition.

You can also make a backup using Disk Utility, but SuperDuper is easier and worked fine even in trial mode. I didn't register yet.

First impressions

• I needed to make space to be able to download the 5 Gb upgrade program, and then some as the first run crashed. At least, I think it was a disk space problem. In any case, after that the second run ran flawlessly. 
• After upgrading I needed to update iMovie and Xcode. Even after that I now have 16 GB free, that was a pleasant surprise!
• I had to restore the Screen Sharing link in my Dock, but just starting it and adding to the dock again was enough.
• While checking out the Notification Center: I saw the edit button at one time, but later it disappeared. Strange, but luckily you can also edit it using Preferences, see http://osxdaily.com/2015/01/30/show-itunes-notification-center-widget-mac-os-x/   
• The 'flatter' style of Yosemite reminded me of the old black and white style of the early Macs, but I admit it does look clean.
• My MBA now connects to the 5Mhz channel. I did need to restart my router to get there. I hope for the last time...
• Calling from my MBA using the iPhone was not working at first. It displayed the message 'devices not on the same Wifi network' but they really were. Tried rebooting and other fixes, no luck. The next day it did work without any changes. This mystery will never be cleared up, I fear.
• On Mavericks, my battery was found to be in 'need of service'. I stil got more than an hour of battery life, so I decided to ignore it. I saw the message disappeared after the upgrade. Not to meaningful, CoconutBattery rates my battery capacity at 61% of the design capacity after 520 cycles. Declining but slowly. No worries.