[eluser]jedd[/eluser]
Hi iamdadude and welcome to the CI forums.
[quote author="iamdadude" date="1266158864"]
I've been developing PHP for a few years now, and CodeIgniter will be pretty much my first framework I've worked with.
[/quote]
This is a common vector - so you're going to be amongst good company. It's a lightweight framework, so tends to be easier to grasp for 'old school' PHP programmers than, say, heavy setups like Zend.
Quote:1. How easy is it to upgrade CI from one version to another?
Upgrade is an overloaded term. Do you mean an extant project you've written, and put into production, and you want to upgrade it? Or do you mean to adopt a new version for new sites, and cope with / learn the new functionality of the new version?
The former - tends to be a non-issue, as security patches are uncommon (not because they're lazy - but because vulnerabilities are rare - one of the benefits of a lightweight framework). In other words, you tend to leave production systems well alone unless you absolutely have to fiddle with them.
Having said that - go read the user guide, and look at the 'upgrade from previous version' link - to get an idea of what's involved. Generally it's very straightforward (painless, simple, fast, low risk).
Quote:2. How well does CI scale my apps?
Can you re-phrase this question please.
Quote:3. Is caching automatic? Are there advanced cache settings?
I think you should read the user guide's section on caching first, maybe dive into the cache code, and then come back with any questions you still have.
Caching is a Big Subject, and there's several layers of it occurring on your average Apache/MySQL/GNU/Linux box, which can make the subject fairly confusing for new users.