I had a psion 3c (not the 5...), and even that was really a small laptop. It could basically do everything the contemporary computers could do except 3d games. The gemini really is a little laptop replacement. With linux, it has a full desktop operating system. In android form, it is a halfway - you can still use it for most things you would use a laptop for. I use it as my only device - I was an original backer and have had it for over 2 months. The keyboard has bedded in well, and is fast and accurate.
The geekbench results for the gemini place it in dual core i5 territory, which is more that fast enough for a laptop replacement for me. For example, the gemini is more than 50% faster than the GPD, 50% faster than an atom x5-z8500, and over twice an x5-8350. The atoms found in most tiny PCs (ie. stick PCs) still make viable PC replacements for on the go use, so by association, so does the gemini. Couple with linux for a full desktop experience. At the initial backer price, there isn't much better. Laptops in the price range are slower and invariably have less storage (32G). I'm sure you could search around and find a better one, but I don't need to anymore.
Granted, Aidan Bell's review shows the gemini is not for everyone but he was one of those people who it is perfect for. He said it the way he saw it, and probably drank the cool-aid early on. It is good he likes his gemini and tells people about it I think.