Start by running SFC and then do a Disk Check on your Windows volume.
Running SFC will ensure that you or a 3rd party application didn't mess up anything that is essential. (Some of the 'Start' replacement programs can move around things or allow you to move around things that shouldn't be messed with.)
For example, if you manually change around default shortcuts in the Start Screen/Menu folders, it can create problems even with system updates, as this are considered 'System' files now and shouldn't be manually messed with.
You could also have issues with permissions in your User folder that some software will erroneously modify. This can slow down the login process as Windows attempts to access a specific folder and then has to give up and use a virtualized location instead.
If this doesn't help, try creating a new account as a test, and then see if it logs in faster.
Not sure if this applies, but on a new upgrade or install, stay logged in for a while so that all the initial optimization can complete.
However, there is nothing different in 8.1 itself that should be causing a delay, in fact it should be faster than 8.0
Also, as strange as this might sound, using a MS Account should be faster, in additional to offering you the full experience of Windows.
A lot of Windows 8.1 functionality depends on a MS Account, even if you aren't big into the Start Screen/Modern Apps, there are other things like IE sync and SkyDrive Sync that help your experience on the desktop. If you have more than one Windows 8/8.1 system that you use, a MS Account will make things really nice as it can keep the majority of your profile sync'd between the systems, which even includes your desktop settings.
Yes, I use a local account and boot straight to the desktop.