Unfortunately I need to use WASAPI loopback recording which was introduced in 2.0.5 so this is a real issue. I have a 3 ghz I7 Windows 7 64 bit computer which usually loads everything in milliseconds.
What I’ve tried that didn’t make a difference:
Ideas?
Is your hard-drive light going nuts while Audacity is trying to start?
How full is the drive?
Absent any known problems, I would remove Audacity and Restart.
Install a fresh download from here.
http://www.audacityteam.org/download/windows/
Part way through, it will ask you if you want to save any of your old settings. Say no.
Koz
I found a solution
Installed 2.1.2 rc3, then made a shortcut to audacity to start minimized and put it in the startup folder as an intended workaround.
Rebooted windows, audacity starts at startup but faster than it used to.
Removed audacity from startup folder, now it starts in a few seconds anyways. weird, but works for me!
My guess is that your anti-virus was scanning Audacity before launching it - perhaps because it was installed by directly running the downloaded exe. Then by moving around different versions of Audacity, your anti-virus has now worked out that Audacity is a known application. This is only conjecture, but it could account for the mystery 
There are probably multiple reasons 2.x is slower. A lot goes on when Audacity launches, such as querying audio devices and looking for LAME and FFmpeg.
1.3.0 did not support FFmpeg, and only used one audio host (MME). 2.x.x has to query audio devices for supported sample rates and other features separately through three hosts (MME, Windows DirectSound and Windows WASAPI). The Windows DirectSound queries are known to cause a slowdown.
1.2.x and 1.3.0 read and wrote a small number of settings directly in the Windows Registry. 2.x.x has lots more settings stored in an audacity.cfg text file.
Do you have a Solid State Drive, grkn? On my Hard Disk Drive system, excluding Audacity from Windows Defender and MalwareBytes Anti-Exploit only saves a few seconds off the 30 seconds to 45 seconds Audacity normally takes to launch.
Gale
Is your hard drive constantly pounding during startup?
Do you have a Solid State Drive, grkn?
Audacity 2.1.2 startup on an SSD system.
1.5 seconds.
Koz
My CPU use goes up from a typical 15% to 35% while Audacity is launching on Windows.
I get about 10 seconds launch time of 2.1.2 on El Capitan, Mac Mini with an HDD.
So much quicker than on Windows.
We know how to make Audacity 2.x.x launch near immediate on Windows, anyway. Don’t do the audio device queries.
Gale
Yes I have a ssd, and no I don’t have any running antivirus.
Same here. Windows 10 x64
Robert
Yes I have a ssd, and no I don’t have any running antivirus.
And over a minute for normal Audacity 2.1.2 startup on an SSD system? That is very wrong.
Time to abandon conventional troubleshooting.
Do you or have you ever edited your Registry?
Koz
Please make sure then that you do very regular anti-virus scans.
Gale