Paypal Redesigned
paypal.com
paypal.com
Seriously, doing a transaction search results in a "please wait" message that reads: "This may take up to 30 seconds".
Anyways, PayPal has been due for an update for a couple years now. As for why it doesn't change when you log in, the main reason PayPal's doing this is to compete with startupy new companies like Square and Stripe in terms of new customer acquisitions. Those new customers won't leave PayPal after tying in their bank accounts, etc., so PayPal isn't as worried about retaining them.
Give it time, there will be a redesign of the logged in view eventually but as it stands I like the logged in view I know it well and it works.
Either way I associate Bootstrap with bold fonts, bold colours whereas this is muted. Reminds me of Kissmetrics actually.
* the dark top bar;
* the blue gradient buttons;
* it's primarily a 1-column layout with a 3-column segment ('buy into being safer' &c.)
None of those Bootstrap-specific, of course, but they are increasingly common as a result of it.