I really like Gnucash and other manual entry financial packages. It's more work to enter them in yourself, but at least they are 100% accurate and don't have to re-authenticate a dozen accounts every day like you often have to do on Personal Capital and the like. No connection issues either which I often have with Personal Capital.
Also online services which attempt to automate things are often not very customizable (like Personal Capital for example with its limitations on categories). I love Gnucash.. I can create as many categories/sub-catogories I want -- called "accounts" and "sub-accounts" in Gnush cash since it's double entry bookkeeping software.
Another huge advantage of Gnucash (and other manual entry financial software packages), is that you can create accounts for all your assets, cash, gift cards, etc.. And do all the bookkeeping for these same as any other account. Online services don't know about your cash transactions, your assets (including tracking appreciation and depreciation), your gift card balances etc. So you still have to manually enter those in, assuming the service offers that -- Personal Capital does not from my experience; and even if they do offer it, from what I have seen it's sloppy implementation, not clean accounting like Gnucash. So with manual entry software packages such as Gnucash, you get a fully accurate accounting of all your accounts and know exactly where everything is going and have more accurate up-to-date balances -- e.g. not having to wait a couple days for transactions to post to see what your current balance is.
I don't know about tracking investments in Gnucash yet. I just am keeping those balances up to date and doing simple debits and credits to them from time to time. I have to see how good Gnucash is tracking funds and stocks etc.. and getting up to date quotes etc. So Personal Capital is still really useful to me in this regard, until I figure this out in Gnucash.
I also do really like the idea of not having all my accounts linked to mint and the like. These for profit companies having access to a record of how much money you having incoming and going out.. what stores you shop at etc.