I'm fairly proficient in C++ and wondered if the tenebrix client was safe to use?
Also if I wanted to review the code myself, are there any warning signs I should look for without studying the code in detail?
There are a lot of people who are hostile to any new crypto-currency, usually because of their vested interest in previous currencies. They tend to audit any new currency's code, looking for things that can embarrass the developers. There's a very good chance that any back door or serious problem would be widely publicized on sites like the Bitcoin forums.
You can certainly audit the changes yourself. Find the closest trusted code base (the one the code you're trying to evaluate is based on), and run a
diff. Then look closely at all changes.
Alternatively, you can rely on the wisdom of crowds. Just wait at least a week or so before accepting any updates published by the development team. And search forums likely to be hostile to that project, such as the Bitcoin forums.