I'm too lazy to convert to/from pounds, but I'd pay $15-20 US for a download if it wasn't DRM crippled and the game looked like it was pretty good. Add $10 or so if it was boxed and the DRM wouldn't bother me as much as long as I could play it on a new GP2X should mine break without having to contact the developers/sellers.
If it is of any help, here are the prices from Craig's poll, converted to USD at the current approximate rate of exchange at the time of writing;
£9.99 (Download), £14.99 (Boxed) = $17.55, $26.34
£14.99 (Download), £19.99 (Boxed) = $26.34, $35.13
£19.99 (Download), £24.99 (Boxed) = $35.13, $43.92
£29.99 (Boxed) = $52.71
As an aside, I would be much more interested in boxed titles than in downloadable ones, as there is both a concern regarding over restrictive DRM (please read further for my reasoning on this issue), and a possible risk with download schemes that there may end up being no way for people on particular operating systems to make use of them. (I am concerned that there would be no way to obtain electronic purchases I make due to the fact that I use Mac OS X, for example.)
Like some others, I would not mind
reasonable DRM on download purchases, as that is only to be expected to protect developers' investments in bringing a game to such an open platform. However, I would be reluctant to take the download route should it mean that my purchases become unusable at some point in the future. My concern over this matter is that if game purchases are tied to a particular SD Card or console unit, and one or both of these things eventually fail (as all things inevitably do), that some games may then become unusable. (Either altogether, or until going through unnecessary hassle to inform merchants or developers that I did indeed purchase a copy of their game, prove that I did, and so on and so forth.)