As promised, we just released a minor maintenance release 1.7.5 that addresses a singular bug with the textile plugin preventing some plugin operations, but only on PHP < 5.3 servers. So if you are running a recent PHP version (like you should...) you will be unaffected by this issue and don't need to upgrade.
The only other change to the previous release is that the spamblock plugin will now add required fields to comments (the comment and the comment's author) when installed for the first time.
Have a nice weekend and greetings from our team :)
- Dirks Logbuch am : Serendipity 1.7.5 ...