I gave up on the alpha build earlier today. After deleting the web cache and cookies and all other stuff and starting Opera again, I found it painfully slow while caching any and all websites, from Hotmail to deviantART.
I remember this happening to me ever since Opera Turbo was introduced, even though I don't use it.
I have a habit of deleting my cache every few days, or as soon as it hits above ~500MB, and I remember uninstalling Opera due to this behavior which haunted me ever since. (I am sure that it wasn't an issue with the current internet speed because IE9 displayed the same webpages much faster, also not having its cache)
I think I might just go ahead and installed 10.63 instead and see how it goes. I'm sick of Google's arrogance, Safari's RAM usage, instability and lack of some features of IE9, Firefox in general, plain weird behavior if Maxthon 3 etc. xD
I should be fair and give Opera one more chance