(Then it leaves us with only TE in the PHP < 5.3 list..? Thorsten, can you elaborate..?)
That's the thing with PHP: some (not all!) changes may be backwards-incompatible. For instance, SMF 2.0.7 is a (pretty underwhelming) patch to mostly improve PHP 5.5 support because the 'e' modifier in PCRE was deprecated, and SMF relied heavily on that. Wedge was patched to the same effect about six months ago (by the same person, I suspect :P). Without these patches, the software would still work, but you'd be getting warnings all over your page. Not cool.
Unfortunately, the reverse is also true... If you try using new PHP features, older versions will give you errors (which isn't a problem for Wedge, except *before* the install process begins, as I painfully noticed today.)
So, basically, whenever you're using software that hasn't been updated in a while (they don't always need to), you're better off staying on your current PHP. All hosts use different ways of allowing users to upgrade; some will force it on them (good luck for old software), and I'm fine with that but I understand it'd be upsetting for those. Some will provide a setting in their panel to choose your default PHP. And some will only enable it if you contact their support team.
So, no worries, it's all good.
That's the whole idea. Wedge forces users to upgrade their PHP to newer, safer versions. If you can update to PHP 5.5, then be my guest. I do all of my local testing on PHP 5.5 these days, so Wedge is fully compatible between PHP 5.3 and 5.5. (5.6 alpha was released recently, and it doesn't break any compatibility in Wedge, so you can add that to the list.)
According to 
