The SQL got updated in Version 3.7. Now the time that it takes to load the data from a mysql database is reasonable. Still not blindingly fast, but comparable to loading from a file. That saved me from setting up a development for Version 3. The last time that I compiled was Version 2. There is a huge difference in required foundation packages.

I have found that the SQL executed to load all the data is extremely inefficient. On my data set, it takes almost 15 minutes to execute the SQL. Using a more efficient SQL statement returns the same data set in <1 second. This query is an ad-hoc statement cobbled together through string concatenation. I'm looking to see where else the function that creates this statement is used to determine if there are unintended consequences for changing the statement.

slow:
`SELECT * FROM slots WHERE obj_guid IN (SELECT DISTINCT guid FROM splits WHERE tx_guid IN (SELECT DISTINCT guid FROM transactions))`

fast:
`SELECT slots.* FROM slots, splits s, transactions t WHERE obj_guid = s.guid AND s.tx_guid = t.guid`

For those users who see an improvement when the locale is set to UTF-8 or C, see https://bugzilla.gnome.org/show_bug.cgi?id=736189.
Also consider just setting a UTF-8 locale instead of an ISO8859 one.

I experienced VERY slow startup of GnuCash 2.6.3 in Linux when the locale environment variable was not set. For me this helped: "export LC_ALL=C; gnucash". Setting LANG=en_US.UTF-8 also worked.

Well, there is a problem no matter what. Admittedly, with open reports it takes much longer, but even without it takes ridiculous amounts of time...

Maybe you have left opened some report or chart tabs and during startup GnuCash rebuilds that report/charts. I have already suggested feature "Lazy report/chart generation during startup":
http://gnucash.uservoice.com/forums/101223-feature-request/suggestions/2628144-lazy-report-chart-generation-during-startup

Try to close your reports and charts before quitting GnuCash and if your next start is much much faster, than please vote for my suggestion.

Thank you.

My experience is similar -- GnuCash is one of the slowest programs to start on my machines.