Regarding the loading times, it's fine after the first time when everything is in the cache. Before that it is painfully slow. It took a good couple of seconds to load the calculator to a functional state on first use and there was a slight loading delay for every tooltip or new weapon choice thereafter. Many of the calculator's competitors are less resource intensive and feel much smoother.
More importantly, the functionality I feel that is missing. Number one on the list is the ability to link secondary weapons. If someone is using a build calculator they are trying to convey enough information to someone else that they can make a functional build. In many if not all builds the secondary weapon set is just as important as the primary. This really really needs to be there for the calculator to be a success.
Secondly on the functionality side of things: Runes, Sigils, Jewels and Amulets. The best build calculator (in my humble opinion) allows you the option of picking these items. This is very useful as you don't have to do the attribute maths yourself and keeps everything in one place. Which brings me to attribute display... another good idea.
I also have a few suggestions as to how to make your calculator a step above the rest:
- Integration with the Guru Forums. Rather than me just seeing a boring hypertext link to a build, I see an image with a summary of the build (e.g. weapon choices and utility slots).
- Allow guide creation along with the build, or at least the ability to link to an external guide. This would be a great way to promote your video system as well.
- Allow the build to be locked with alternatives. For example, at top tier SPvP you might be using two weapons (primary and secondary), but switch the secondary weapon out for a third weapon on occasion. If you gave the calculator the ability to somehow list the third weapon as the preferred alternative to the secondary weapon, that would make the calculator much better. This would also allow people to customize optional parts of a build to their liking.