Best
Discover - both online and mobile, beautiful site, easy to navigage, the mobile app is especially impressive
American Express - love the color scheme, very clean, all necessary functionality is there, but it's got a couple of minor bugs
Chase - not pretty to look at, but all necessary functionality is there
Barclays - website is very aesthetically pleasing; mobile app is junk, was much better before it was "updated" late last year
Worst
Citi - in this day and age, no pending transactions
FIA - outdated as hell, but back in 2005 it was the first site I ever saw that actually showed pending transactions
U.S. Bank - before recent makeover, a throwback to the glorious days of Web 1.0; after makeover, make a payment, wonder why it doesn't show up in pending payments
Best for me are Discover and BofA since I like the luv button front and center 
not buried somewhere in a bunch of links like on US Bank and Citi. 
My best and worst for my lineup are as follows:
Online Best: My credit union website. Functionality and aesthetics are top notch. American Express would be second.
Online Worst: If I had to choose, it would be Capital One. Suprisingly, I like all of the online websites I have to use for my accounts. But I like this one the least.
Mobile Best: American Express. Looks great and has everything I need within one-click. I do like the "SureSwipe" login feature for the Capital One app though.
Mobile Worst: Bank of America. I don't like using this app for some reason and I hate the way it looks. This is becoming my favorite card though.
@CenturyChild wrote:No clue about Discover as I do not have one but ...
So far Barclay is one of the best laid out sites I have.
2nd would be CapOne for me.
I know many seem to hate it but for whatever reason I dont have issues with it.
Simple and easy to navigatye my accounts and find the info I need.
Worst --- Another Chase vote. Too many clickys to find what Im looking for.
GE Capital isn't bad but its very plain. Easy to navigate and all the important stuff is easy to get to ..
I like them better than Chases layout as well.
+1
@Gunnar419 wrote:
@bk510 wrote:
@trumpet-205 wrote:I have to say the worst in my experience is Capital One. The website is unstable from time to time.
Not for me, It hasnt.
They just upgraded their site very recently and I like said earliar, Its not pretty but pretty easy to navigate.
I like CapOne since the upgrade, too. It's not my favorite, but it's pretty decent, and I've also never had a problem with instability.
+1
@thelethargicage wrote:Best
Discover - both online and mobile, beautiful site, easy to navigage, the mobile app is especially impressive
American Express - love the color scheme, very clean, all necessary functionality is there, but it's got a couple of minor bugs
Chase - not pretty to look at, but all necessary functionality is there
Barclays - website is very aesthetically pleasing; mobile app is junk, was much better before it was "updated" late last year
Worst
Citi - in this day and age, no pending transactions
FIA - outdated as hell, but back in 2005 it was the first site I ever saw that actually showed pending transactions
U.S. Bank - before recent makeover, a throwback to the glorious days of Web 1.0; after makeover, make a payment, wonder why it doesn't show up in pending payments
+1,
I'm happy for US BANK folks.... It's bout time.
@DigitalArk wrote:Best:
USAA
Amex
Discover
Barclays
Worst:
Chase
NFCU
For NFCU...
1. Their recurring transfer drives me crazy. It auto transferred money from my NFCU checking to my cashRewards on the day I had it set up even though I chose statement balance. It's never on the due day. The worst thing was that it still transferred money when my balance was zero. My account used to have negative balance every month until I canceled the auto recurring transfer.
2. You cannot set up auto pay your statement balance with an external checking account. I asked them about that via secure message:
Your Message 03/24/2014 : Is there any plan to implement the feature of auto paying credit card statement balance with an external checking account? It will be such a great help to me if so and I will not hesitate to switch my main spending credit card to cashRewards or even upgrade to Flagship Rewards. Currently, it is the only reason holding me up.
Navy Federal Response 03/24/2014 : Thank you for your message. An ACH debit is an electronic preauthorized debit processed through the Automated Clearing House. For security reasons, we are unable to provide account access to third parties. As a result, we are unable to provide the statement balance to your financial institution. We apologize for any inconvenience this may have caused.
To set up recurring payment transfers to your Navy Federal credit card account from a checking account at another financial institution, click on the Transfers icon on the navigation bar at the top of your screen. Then, select Transfer Funds to/from Another Financial Institution. If the checking account is already registered as an external account, you may select One-Time Transfer or Recurring Transfer from the Make a Transfer option. If the checking account is not in your list of external accounts, you must select Register External Account under the External Accounts option. On the next screen, complete the required information and click on I want to register. A letter containing your registration code will be mailed to your address of record. To request an external transfer prior to receiving your registration code letter, please contact any Navy Federal branch or call us toll-free any time at 1-888-842-6328. Alternatively, you may provide the checking account and routing numbers to debit at the other financial institution, your Navy Federal credit card account number to credit, the payment amount to transfer and the transfer date via fax number 703-206-3319. Be sure to sign your request, since unsigned documents will not be processed. Once you have received your registration code, you may make a one-time transfer, schedule a future dated transfer or establish a recurring transfer online. Please note that the owner of the account to be debited must be the owner of the credit card account to be credited.
If you have any further questions or concerns, please let us know.
3. Their CC reward programs suck. I am actually thinking to close my cashRewards even though it has 18.5K limit. The reason why I am still keeping it is because I want to build a solid relationship with NFCU. But I think I can just do that with depository accounts, CC is not necessary. Am I correct?
+1
Couldnt argue with that. I would also throw Cap1 while I'm at it