Take a look at the website of your favorite multinational brand - what do you see? Odds are there are hot visual effects and maybe even a customized application, both of which take that much longer to load not to mention the fact that search engine bots have no idea why they are there. To remain competitive from an SEO standpoint, site performance is a critical issue on two fronts:
Sure, we can enjoy our time on our high-speed broadband connections, but not everybody can enjoy this benefit. As a result, search engines take into account the speed with which a website performs for two reasons. First, search engines do not cater only to high-speed connections but also the dial-up users in the third world. Because search engines are interested in providing useful content, speed is an issue. Second, some less-than-ingenious web hosts are utilizing a method for throttling bot traffic to app-heavy websites to save on bandwidth. Rather than returning the actual page to the bot for scanning, the server throws out an internal error code. Care to guess how many visitors appear on a website that bots think is out of order?
The second reason site performance is critical to SEO competitiveness is that bots are artificial intelligence with barely any intelligence at all in a comparative sense. I say this because the amount of HTML/text-based content on webpages is shrinking while application/image-based content is growing despite the fact that bots can only read HTML/text. Go back to the multinational brand website you visited earlier and see how much of the content - even text meant to be read - is displayed as graphics rather than straight text. Bots don't see the value in the cool text effects and slide shows because they can't read the image. Hence, the valuable SEO keywords are lost in favor of user-targeted site performance. If a compromise must be made on apps and images, make it this: put as much text as possible on the page in an SEO-friendly way. Cool effects may reduce bounce rates, but SEO gets users on the page in the first place!
So, a faster page that works within the limits of search bots is the way to go when SEO competitiveness is concerned. Avoid the temptation to pimp your page and keep SEO at the front of your mind and you will be in good shape.