I've been using ING Direct for years now, but I've finally decided to move to a higher yielding online savings/money market account. ING Direct recently lowered their yield to 2.75%.
On top of that, two other restrictions dissuade me from sticking with them:
1. They don't allow me to link to my Fidelity accounts, even through the associated United Missouri Bank checking accounts. They used to allow this and I do have a link setup to one of my Fidelity accounts, but when I went to add a link to my main Fidelity account, they said it wasn't possible. I went ahead and tried anyway, treating it like a United Missouri Bank account (this is the bank that Fidelity uses for checks associated with the Fidelity brokerage accounts), but they rejected it. I thought perhaps that they would treat this UMB account just like any other checking account, but for some reason it is treated differently.
2. I can't update Quicken as easily as I can my other bank and brokerage accounts. ING Direct is the only bank account that I have that requires me to login through their website and download the data (using Quicken's Web Connect feature). My other banks let me just setup their accounts as part of a one-step account update procedure that automatically downloads the account data (Quicken calls this their Direct Connect feature).
I'm having difficulty determining which online savings accounts allow me to download data directly into Quicken, but I'm leaning towards opening a new account at either Capital One Online Savings (through Costco) for 3.66% rate or perhaps trying out DollarSavingsDirect. I'll post a followup here once I've opened a new account.